UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                               ------------------

                                    FORM 11-K

                               ------------------

                     ANNUAL REPORT PURSUANT TO SECTION 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


(Mark one)

[X]  ANNUAL report pursuant to section 15(d) of the Securities Exchange Act of
     1934

     For Fiscal year ended December 31, 2006

                                       or

[_]  Transition report pursuant to Section 15(d) of the Securities Exchange Act
     (No fee required)

             For the transition period from _________ to ___________

Commission file number 001-10533


A.   Full title of the plan and the address of the plan, if different from that
     of the issuer named below:

                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES

B.   Name of issuer of the securities held pursuant to the Plan and the address
     of its principal executive office:

         Rio Tinto plc, 6 St. James's Square, London, SW1Y 4LD, England



                                  Page 1 of 22






                    U.S. BORAX INC.
                    401(k) PLAN FOR HOURLY EMPLOYEES

                    FINANCIAL STATEMENTS AND SUPPLEMENTAL SCHEDULE

                    AS OF DECEMBER 31, 2006 AND 2005
                    AND FOR THE YEAR ENDED DECEMBER 31, 2006

                    TOGETHER WITH REPORT OF INDEPENDENT REGISTERED PUBLIC
                    ACCOUNTING FIRM










                                  Page 2 of 22




                                                                 U.S. BORAX INC.
                                                401(k) PLAN FOR HOURLY EMPLOYEES
                                                               TABLE OF CONTENTS
--------------------------------------------------------------------------------


                                                                            PAGE
                                                                            ----

Report of Independent Registered Public Accounting Firm                       4

Financial Statements:

     Statements of Net Assets Available for Benefits as of
       December 31, 2006 and 2005                                             6

     Statement of Changes in Net Assets Available for Benefits
       for the year ended December 31, 2006                                   7

     Notes to Financial Statements                                       8 - 17

Supplemental Schedule - Schedule H, Part IV, line 4i -
  Schedule of Assets (Held at End of Year) as of December 31, 2006      18 - 19

Signature                                                                    20

Exhibits                                                                     21

All other schedules required by Section 2520.103-10 of the Department of Labor's
Rules and Regulations for Reporting and Disclosure under the Employee Retirement
Income Security Act of 1974 have been omitted because they are not applicable to
the U.S. Borax Inc. 401(k) Plan for Hourly Employees.






                                  Page 3 of 22


                                               215 South State Street, Suite 800
                                                      Salt Lake City, Utah 84111
                                                        Telephone (801) 532-7444
                                                              Fax (801) 532-4911
                                                                www.tannerco.com
--------------------------------------------------------------------------------
[TANNER LC LOGO]


                                         REPORT OF INDEPENDENT REGISTERED PUBLIC
                                                                 ACCOUNTING FIRM

Plan Administrator
U.S. Borax Inc. 401(k) Plan for Hourly Employees

We have audited the accompanying statements of net assets available for benefits
of the U.S. Borax Inc. 401(k) Plan for Hourly Employees (the Plan) as of
December 31, 2006 and 2005, and the related statement of changes in net assets
available for benefits for the year ended December 31, 2006. These financial
statements are the responsibility of the Plan's management. Our responsibility
is to express an opinion on these financial statements based on our audits.

We conducted our audits in accordance with the standards of the Public Company
Accounting Oversight Board (United States). Those standards require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements are free of material misstatement. An audit includes consideration of
internal control over financial reporting as a basis for designing audit
procedures that are appropriate in the circumstances, but not for the purpose of
expressing an opinion on the effectiveness of the Plan's internal control over
financial reporting. Accordingly, we express no such opinion. An audit includes
examining, on a test basis, evidence supporting the amounts and disclosures in
the financial statements. An audit also includes assessing the accounting
principles used and significant estimates made by management, as well as
evaluating the overall financial statement presentation. We believe that our
audits provide a reasonable basis for our opinion.

In our opinion, the financial statements referred to above present fairly, in
all material respects, the net assets available for benefits of the U.S. Borax
Inc. 401(k) Plan for Hourly Employees as of December 31, 2006 and 2005, and the
changes in net assets available for benefits for the year ended December 31,
2006, in conformity with U.S. generally accepted accounting principles.

As described in Note 2, the Plan adopted Financial Accounting Standards Board
Staff Position AAG INV-1 and SOP 94-4-1, Reporting of Fully Benefit-Responsive
Investment Contracts Held by Certain Investment Companies Subject to the AICPA
Investment Company Guide and Defined-Contribution Health and Welfare and Pension
Plans, as of December 31, 2006.



                                  Page 4 of 22


Our audits of the financial statements were performed for the purpose of forming
an opinion on the basic financial statements taken as a whole. The supplemental
Schedule of Assets (Held at End of Year) as of December 31, 2006, is presented
for the purpose of additional analysis and is not a required part of the basic
financial statements, but is supplementary information required by the United
States Department of Labor's Rules and Regulations for Reporting and Disclosure
under the Employee Retirement Income Security Act of 1974. The supplemental
schedule is the responsibility of the Plan's management and has been subjected
to the auditing procedures applied in the audit of the basic financial
statements and, in our opinion, is fairly stated in all material respects in
relation to the basic financial statements taken as a whole.



/s/ Tanner LC

Salt Lake City, Utah
June 29, 2007






                                  Page 5 of 22


                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                 STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS

                                                                    DECEMBER 31,
--------------------------------------------------------------------------------


                                                                   (AS RESTATED)
                                                            2006        2005
                                                       -------------------------
     ASSETS
     ------

Investments (at fair value)                            $39,227,723   $35,165,636
                                                       -------------------------

Receivables:
  Employee contributions                                    93,458       108,479
  Employer contributions                                    13,781        15,763
                                                       -------------------------

          Total receivables                                107,239       124,242
                                                       -------------------------

          Total assets                                  39,334,962    35,289,878

     LIABILITIES
     -----------

Excess contributions payable                                10,993        29,453
                                                       -------------------------

Net assets available for benefits (at fair value)       39,323,969    35,260,425

Adjustment from fair value to contract value for
  fully benefit-responsive investment contracts            225,578       154,489
                                                       -------------------------

Net assets available for benefits                      $39,549,547   $35,414,914
                                                       =========================

--------------------------------------------------------------------------------
See accompanying notes to financial statements.



                                  Page 6 of 22


                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                       STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

                                                    YEAR ENDED DECEMBER 31, 2006
--------------------------------------------------------------------------------


ADDITIONS TO NET ASSETS ATTRIBUTED TO:
  Investment income:
    Net appreciation in fair and contract values of investments      $ 1,605,385
    Interest and dividends                                             1,934,963
                                                                     -----------

          Total investment income                                      3,540,348
                                                                     -----------

Contributions:
  Employee                                                             2,638,806
  Employer                                                               368,364
                                                                     -----------

          Total contributions                                          3,007,170
                                                                     -----------

          Total additions                                              6,547,518
                                                                     -----------

DEDUCTIONS FROM NET ASSETS ATTRIBUTED TO:
  Benefits paid to participants                                        2,088,796
  Transfer to the Rio Tinto America Inc. Savings Plan                    323,270
  Administrative expenses                                                    819
                                                                     -----------

          Total deductions                                             2,412,885
                                                                     -----------

Increase in net assets available for benefits                          4,134,633

NET ASSETS AVAILABLE FOR BENEFITS:
  Beginning of year                                                   35,414,914
                                                                     -----------

  End of year                                                        $39,549,547
                                                                     -----------

--------------------------------------------------------------------------------
See accompanying notes to financial statements.



                                  Page 7 of 22


                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS

--------------------------------------------------------------------------------

1.   DESCRIPTION OF          The following  brief  description of the U.S. Borax
     THE PLAN                Inc. 401(k) Plan for Hourly Employees (the Plan) is
                             provided  for general  information  purposes  only.
                             Participants  should refer to the Plan document and
                             summary   plan   description   for  more   complete
                             information.

                             GENERAL
                             The Plan is a defined  contribution  plan  covering
                             full-time  hourly  employees who are represented by
                             or included in a collective bargaining unit of U.S.
                             Borax Inc. and its  affiliates  (collectively,  the
                             "Company"),  as defined in the Plan document.  U.S.
                             Borax Inc. is an indirect,  wholly-owned subsidiary
                             of Rio Tinto  America  Inc.,  which is an indirect,
                             wholly-owned  subsidiary  of  Rio  Tinto  plc  (the
                             Parent).  The Plan is  intended  to be a  qualified
                             retirement  plan under the  Internal  Revenue  Code
                             (IRC)  and  is  subject  to the  provisions  of the
                             Employee  Retirement  Income  Security  Act of 1974
                             (ERISA), as amended.

                             Effective January 1, 2005,  eligible  employees who
                             are    represented   by   Local    30-International
                             Longshoremen's  and  Warehousemen's   Union  (Boron
                             hourly  employees)  can  participate  in  the  Plan
                             immediately   after   completing   sixty   days  of
                             continuous service.

                             Eligible  employees  who are  represented  by Local
                             20A-International Longshoremen's and Warehousemen's
                             Union (Wilmington hourly employees) can participate
                             in the Plan immediately upon employment.

                             CONTRIBUTIONS
                             Each year,  participants  may elect  under a salary
                             reduction  agreement  to  contribute  to the  Plan.
                             Contributions   are  limited  by  the  IRC,   which
                             established a maximum  contribution  of $15,000 for
                             the  year  ended  December  31,  2006.  Participant
                             contributions  are  recorded  in the period  during
                             which the amounts  are  withheld  from  participant
                             earnings.  Participants may also contribute amounts
                             representing  distributions  from  other  qualified
                             defined benefit or defined contribution plans.

--------------------------------------------------------------------------------



                                  Page 8 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------

1.   DESCRIPTION OF          CONTRIBUTIONS - CONTINUED
     THE PLAN                Effective  January 1, 2005,  Boron hourly employees
     CONTINUED               can  contribute  an amount not less than 1% and not
                             more than 30% of their eligible  compensation  on a
                             before-tax   basis  through   payroll   deductions.
                             Participants  may also  elect to make an  after-tax
                             contribution not less than 1% and not more than 30%
                             of their eligible  compensation.  Total  before-tax
                             and  after-tax  contributions  cannot exceed 30% of
                             participants' eligible compensation.

                             The  Company   matches   the  Boron   participants'
                             contributions  to the Plan at 30%,  up to the first
                             5%  of  their   eligible   compensation.   Matching
                             contributions  are recorded on the date the related
                             participant contributions are withheld.

                             Wilmington   hourly  employees  can  contribute  an
                             amount  not less  than 1% and not more  than 15% of
                             their eligible  compensation on a before-tax  basis
                             through payroll  deductions.  Participants may also
                             elect to make an  after-tax  contribution  not less
                             than 1% and not more  than  15% of  their  eligible
                             compensation.   Total   before-tax   and  after-tax
                             contributions  cannot  exceed 15% of  participants'
                             eligible compensation.

                             The Company  matched the  Wilmington  participants'
                             contributions  to the Plan at 30%,  up to the first
                             5% of their eligible  compensation through June 16,
                             2005.  Effective June 17, 2005, the Company matches
                             the Wilmington  participants'  contributions to the
                             Plan at 35%,  up to the first 5% of their  eligible
                             compensation.  Matching  contributions are recorded
                             on the date the related  participant  contributions
                             are withheld.

                             PARTICIPANT ACCOUNTS
                             Individual  accounts are  maintained  for each Plan
                             participant. Each participant's account is credited
                             with the participant's contributions, the Company's
                             matching  contributions,  and an  allocation of the
                             Plan's  earnings,  and is charged with  withdrawals
                             and  an   allocation   of  the  Plan's  losses  and
                             administrative  expenses.  Allocations are based on
                             participant   earnings  or  account  balances,   as
                             defined.  The  benefit  to which a  participant  is
                             entitled is the benefit  that can be provided  from
                             the participant's vested account.

--------------------------------------------------------------------------------



                                  Page 9 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


1.   DESCRIPTION OF          PARTICIPANT-DIRECTED OPTIONS FOR INVESTMENTS
     THE PLAN                Participants   direct  the   investment   of  their
     CONTINUED               contributions     and    the    Company    matching
                             contributions   into  various   investment  options
                             offered by the Plan.  Investment  options include a
                             money market fund, common collective trusts, mutual
                             funds,  guaranteed investment contracts,  synthetic
                             guaranteed investment contracts and common stock of
                             the  Parent  in the  form  of  American  Depository
                             Receipts (ADRs).

                             VESTING
                             Participants   are  immediately   vested  in  their
                             contributions  and Company  matching  contributions
                             plus actual earnings thereon.

                             PAYMENT OF BENEFITS
                             On termination of service due to death, disability,
                             or retirement,  participants or their beneficiaries
                             may  elect to  receive  lump-sum  distributions  or
                             annual,    semi-annual,    quarterly   or   monthly
                             installments  in amounts  equal to the value of the
                             participants'  vested  interests in their accounts.
                             Under  certain   circumstances,   participants  may
                             withdraw   their   contributions   prior   to   the
                             occurrence of these events.

                             TRANSFERS
                             Along  with the Plan,  the  Company  also  sponsors
                             other   401(k)   plans   that   cover   represented
                             employees.  If employees  are changed from union to
                             non-union  status  during the year,  their  account
                             balances  are  transferred  from  this  Plan to the
                             non-union  plan.  For the year ended  December  31,
                             2006,  transfers  to the  Rio  Tinto  America  Inc.
                             Savings Plan totaled $323,270.

2.   SUMMARY OF              BASIS OF PRESENTATION
     SIGNIFICANT             The  financial  statements  of the Plan  have  been
     ACCOUNTING              prepared on the accrual basis of accounting.
     POLICIES

--------------------------------------------------------------------------------



                                  Page 10 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


2.   SUMMARY OF              USE OF ESTIMATES
     SIGNIFICANT             The preparation of the Plan's financial  statements
     ACCOUNTING              in conformity with accounting  principles generally
     POLICIES                accepted in the United  States of America  requires
     CONTINUED               Plan  management to make estimates and  assumptions
                             that  affect  the  reported  amounts  of net assets
                             available for benefits at the date of the financial
                             statements, the changes in net assets available for
                             benefits  during the  reporting  period  and,  when
                             applicable,  the  disclosures of contingent  assets
                             and  liabilities  at  the  date  of  the  financial
                             statements.  Actual results could differ from those
                             estimates.

                             ADOPTION OF NEW FINANCIAL ACCOUNTING STANDARD
                             In  December   2005,   the   Financial   Accounting
                             Standards  Board ("FASB")  issued a Staff Position,
                             ("FSP"),  Reporting  of  Fully  Benefit  Responsive
                             Investment  Contracts  Held by  Certain  Investment
                             Companies  Subject to the AICPA Investment  Company
                             Guide and  Defined-Contribution  Health and Welfare
                             and Pension Plans.  This FSP amends the guidance in
                             AICPA  Statement  of Position  94-4,  Reporting  of
                             Investment  Contracts  Held by Health  and  Welfare
                             Benefits  Plans and  Defined-Contribution  Pensions
                             Plans,  with  respect  to the  definition  of fully
                             benefit-responsive  investment  contracts  and  the
                             presentation     and     disclosure     of    fully
                             benefit-responsive  investment  contracts  in  Plan
                             financial   statements.   The  FSP  requires   that
                             investments in fully benefit-responsive  investment
                             contracts   be  presented  at  fair  value  in  the
                             statement of net assets  available for benefits and
                             that the amount representing the difference between
                             fair value and contract value of these  investments
                             also be presented  on the face of the  statement of
                             net  assets  available  for  benefits.  The  FSP is
                             effective  for  financial   statements  for  annual
                             periods ending after December 15, 2006, and must be
                             applied   retroactively   to  all   prior   periods
                             presented.  Accordingly,  the Plan has  adopted the
                             financial  statement  presentation  and  disclosure
                             requirements  effective  December 31, 2006, and has
                             restated the 2005 Statement of Net Assets Available
                             for  Benefits  to present all  investments  at fair
                             value,   with  the  adjustment  to  contract  value
                             separately  disclosed.  The effect of adopting  the
                             FSP  had  no  impact  on  the   Plan's  net  assets
                             available  for  benefits  or  changes in net assets
                             available for benefits,  as such  investments  have
                             historically  been  presented  at  contract  value.
                             Refer to Note 3 for additional  information related
                             to the Plan's fully  benefit-responsive  investment
                             contracts.


--------------------------------------------------------------------------------



                                  Page 11 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


2.   SUMMARY OF              RISKS AND UNCERTAINTIES
     SIGNFIICANT             The Plan  provides for  investments  in  securities
     ACCOUNTING              that are exposed to various risks, such as interest
     POLICIES                rate,  currency  exchange rate,  credit and overall
     CONTINUED               market  fluctuation.  Due  to  the  level  of  risk
                             associated with certain investment  securities,  it
                             is  reasonably  possible that changes in the values
                             of  investment  securities  will  occur in the near
                             term and that such changes could materially  affect
                             participants'  account  balances  and  the  amounts
                             reported in the statements of net assets  available
                             for benefits.

                             INVESTMENT VALUATION AND INCOME RECOGNITION
                             The Plan's  investments  in mutual funds are valued
                             at quoted market  prices,  which  represent the net
                             asset  value of units held by the Plan at year end.
                             Plan investments in common stock are stated at fair
                             value  based on quoted  market  prices.  The Plan's
                             interest in the Dwight  Stable Value Fund is valued
                             based  upon  the  market  value  of the  underlying
                             securities  at quoted  market value or quoted share
                             prices.  Participant  loans  are  valued  at  their
                             outstanding balances, which approximate fair value.

                             Purchases and sales of securities are recorded on a
                             trade-date basis. Interest income is recorded on an
                             accrual  basis.   Dividends  are  recorded  on  the
                             ex-dividend date.

                             The net  appreciation  (depreciation)  in the  fair
                             value of investments  which includes realized gains
                             (losses) and unrealized appreciation (depreciation)
                             on those  investments  is shown in the statement of
                             changes in net assets available for benefits of the
                             Plan.

                             PAYMENTS OF BENEFITS
                             Benefit  payments  are  recorded  when  paid by the
                             Plan.

--------------------------------------------------------------------------------



                                  Page 12 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


2.   SUMMARY OF              ADMINISTRATIVE EXPENSES
     SIGNIFICANT             The  Company  pays the  majority  of the  costs and
     ACCOUNTING              expenses  incurred in  administering  the Plan. The
     POLICIES                Plan has  several  fund  managers  that  manage the
     CONTINUED               investments held by the Plan. During the year ended
                             December 31, 2006,  the Company paid all investment
                             management fees related to the Plan.

                             The   investment   management   fees   related   to
                             transaction  costs  associated with the purchase or
                             sale  of  Rio  Tinto  plc  ADRs  are  paid  by  the
                             participants.

                             PARTICIPANT LOANS
                             Participants  may  borrow  from  the  Plan  up to a
                             maximum  of   $50,000  or  50%  of  their   account
                             balances,  whichever is less.  Each loan is secured
                             by the  balance in the  participant's  account  and
                             bears   interest  at  a  rate   commensurate   with
                             prevailing rates at the time funds are borrowed, as
                             determined   by  the  Plan   Administrator.   Loans
                             originated  during the year ended December 31, 2006
                             have interest  rates set at prime plus one percent,
                             and are reset quarterly.

--------------------------------------------------------------------------------



                                  Page 13 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


3.   FULLY BENEFIT           The Plan's  investments  include the Dwight  Stable
     RESPONSIVE              Value  Fund.   The  Dwight  Stable  Value  Fund  is
     INVESTMENT              invested   in  a  money   market   fund,   a  fully
     CONTRACTS               benefit-responsive common collective trust (the SEI
                             Stable  Asset Fund),  and fully  benefit-responsive
                             synthetic guaranteed investment contracts (GICs).

                             Synthetic  GICs provide for a guaranteed  return on
                             principal  over a specified  period of time through
                             fully benefit-responsive wrap contracts,  issued by
                             a third  party,  which are  secured  by  underlying
                             assets.  The  portfolio  of assets  underlying  the
                             synthetic  GICs has an overall  AAA credit  quality
                             and includes mortgages, fixed income securities and
                             United States treasury notes and bonds.

                             The wrap  contracts  are  obligated  to  provide an
                             interest rate not less than zero.  These  contracts
                             typically  provide  that  realized  and  unrealized
                             gains and losses on the  underlying  assets are not
                             reflected  immediately  in the  net  assets  of the
                             fund.  Realized and unrealized gains and losses are
                             amortized, usually over the time to maturity or the
                             duration  of the  underlying  investments,  through
                             adjustments to the future interest crediting rate.

                             The  contract or crediting  interest  rates for the
                             GICs are typically reset quarterly and are based on
                             the  market  value  of  the   portfolio  of  assets
                             underlying   these   contracts.   Inputs   used  to
                             determine the crediting interest rates include each
                             contract's    portfolio   market   value,   current
                             yield-to-date maturity,  duration, and market value
                             relative to contract value.

                             These wrap contracts  provide  benefit  withdrawals
                             and investment exchanges at the full contract value
                             of the synthetic contracts  (principal plus accrued
                             interest)  notwithstanding  the actual market value
                             of the  underlying  investments  (fair  value  plus
                             accrued interest).
--------------------------------------------------------------------------------



                                  Page 14 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


3.   FULLY BENEFIT           Certain events may limit the ability of the Plan to
     RESPONSIVE              transact at contract value with the issuer of fully
     INVESTMENT              benefit-responsive   investment   contracts.   Such
     CONTRACTS               events include the following: (1) amendments to the
     CONTINUED               Plan documents  (including complete or partial plan
                             termination  or  merger  with  another  plan),  (2)
                             bankruptcy  of  the  Plan  sponsor  or  other  Plan
                             sponsor  events  (for  example,   divestitures   or
                             spin-offs of a subsidiary) that cause a significant
                             withdrawal from the Plan, or (3) the failure of the
                             trust to qualify for exemption  from federal income
                             taxes  or  any  required   prohibited   transaction
                             exemption  under  ERISA,   as  amended.   The  Plan
                             Administrator  does not believe that the occurrence
                             of any such  event,  which  would  limit the Plan's
                             ability  to  transact   at   contract   value  with
                             participants, is probable.

                             The contracts  provide that withdrawals  associated
                             with  certain  events which are not in the ordinary
                             course of fund  operations,  and are  determined by
                             the issuer to have a material adverse effect on the
                             issuer's financial  interest,  may be paid at other
                             than contract value.

                             Average  duration for all investment  contracts was
                             2.93 and 2.93 years at December  31, 2006 and 2005,
                             respectively.  Average  yield  data  for all  fully
                             benefit -  responsive  investment  contracts  as of
                             December 31, 2006 and 2005 was as follows:

                             AVERAGE YIELDS:                    2006    2005
                             ---------------------------------------------------
                             Based on actual earnings           5.04%   4.65%
                             Based on interest rate credited
                               to participants                  5.08%   4.71%

--------------------------------------------------------------------------------



                                  Page 15 of 22


                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


4.   RELATED PARTY           Certain  Plan  investments  are  managed  by Putnam
     TRANSACTIONS            Investments,  the Plan  trustee,  therefore,  these
                             transactions    are    exempt     party-in-interest
                             transactions. Transaction fees paid by the Plan for
                             investment  management  services were included as a
                             reduction of the return earned on each fund.

                             Transactions associated with Rio Tinto plc ADRs are
                             considered  exempt  party-in-interest  transactions
                             because Rio Tinto plc is the parent of the Company.
                             As of  December  31,  2006 and 2005,  the Plan held
                             13,357 and 12,956 shares,  respectively,  of common
                             stock  of Rio  Tinto  plc,  with a  cost  basis  of
                             $1,617,230 and $1,288,479, respectively. During the
                             year ended  December  31, 2006,  the Plan  recorded
                             dividend income of $103,869 related to this stock.

                             At December 31, 2006 and 2005,  the Plan held loans
                             from   participants    totaling    $2,611,022   and
                             $2,552,318,  respectively. Loans to particpants, at
                             cost,  which   approximates   fair  value,  are  at
                             interest   rates   ranging   from  5%  to  10%  and
                             have maturities ranging from 2007 to 2015.

5.   INVESTMENTS             The  Plan's  investments  stated at fair value that
                             represent  five  percent  or more of the Plan's net
                             assets  available  for  benefits as of December 31,
                             2006 and 2005 are as follows:

                                                              2006       2005
                                                           ---------   ---------

                             SEI Stable Asset Fund        $7,436,509  $7,710,657
                             Dodge & Cox Stock Fund        5,382,138   4,715,932
                             Putnam Voyager Fund           3,581,426   3,761,446
                             State Street Bank
                               Synthetic GIC               3,513,183   2,621,455
                             Monumental Life Insurance
                               Company Synthetic GIC       3,513,183   2,621,455
                             Rio Tinto plc American
                               Depository Shares           2,838,223   2,368,229
                             Participant Loans             2,611,022   2,552,318
                             Artisan Mid Cap Fund          2,600,333   2,436,109
                             Putnam S&P 500 Index Fund     2,314,472   2,158,749
--------------------------------------------------------------------------------



                                  Page 16 of 22



                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                   NOTES TO FINANCIAL STATEMENTS
                                                                       CONTINUED
--------------------------------------------------------------------------------


5.   INVESTMENTS             During the year ended December 31, 2006, the Plan's
     CONTINUED               investments   (including   gains   and   losses  on
                             investments bought and sold, as well as held during
                             the year) appreciated in value as follows:

                                 Mutual funds                        $   891,058
                                 Common stock                            381,673
                                 Common collective trusts                332,654
                                                                     -----------

                                 Net appreciation in investments     $ 1,605,385
                                                                     ===========

6.   PLAN                    Although it has not  expressed  any intention to do
     TERMINATION             so,  the  Company  has the right  under the Plan to
                             discontinue  its  contributions  at any time and to
                             terminate  the Plan subject to the  provisions  set
                             forth in ERISA.


7.   INCOME TAX              The Internal  Revenue  Service has  determined  and
     STATUS                  informed  the Company by a letter  dated August 27,
                             2003, that the Plan and related trust were designed
                             in accordance  with the applicable  requirements of
                             the  Internal  Revenue  Code.  The  Plan  has  been
                             amended since receiving the  determination  letter;
                             however,  the  Plan  Administrator  and the  Plan's
                             legal  counsel  believe  that the Plan is currently
                             designed and being operated in compliance  with the
                             applicable  requirements  of the  Internal  Revenue
                             Code. Therefore,  no provision for income taxes has
                             been included in the Plan's financial statements.

8.   RECONCILIATION          The  following  is a  reconciliation  of net assets
     OF FINANCIAL            available   for   benefits  as   presented  in  the
     STATEMENTS TO           financial statements as of December 31, 2006 to the
     FORM 5500               Form 5500:

                                Net assets available for benefits
                                  as presented in the financial
                                  statements                       $ 39,549,547

                                Adjustment from fair value to
                                  contract value
                                  For fully benefit-responsive
                                  investment Contracts                 (225,578)
                                                                   ------------

                                Net assets available for benefits
                                  as presented in Form 5500        $ 39,323,969
                                                                   ============

--------------------------------------------------------------------------------



                                  Page 17 of 22





                                                                                    U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                                                          EMPLOYER IDENTIFICATION NUMBER: 98-0047580
                                                                                                                    PLAN NUMBER: 007
                                                                                                        SCHEDULE H, PART IV, LINE 4I
                                                                                            SCHEDULE OF ASSETS (HELD AT END OF YEAR)

                                                                                                                   DECEMBER 31, 2006
------------------------------------------------------------------------------------------------------------------------------------

  (a)                 (b)                                     (c)                                         d)            (e)
PARTY IN                                                                                   NUMBER OF                  CURRENT
INTEREST       IDENTITY OF ISSUER                   DESCRIPTION OF INVESTMENT                UNITS       COST          VALUE
--------   ---------------------------   ----------------------------------------------   -----------    ----   --------------------

                                                                                                   
                                         MONEY MARKET FUND:
           Mellon Bank                   Mellon Bank - STIF Account                         25,806        **       $   25,806
                                                                                                                --------------------

                                         COMMON COLLECTIVE TRUSTS:
           SEI Investments               SEI Stable Asset Fund                                            **        7,436,509
   *       Putnam                        Putnam S&P 500 Index Fund                          62,267        **        2,314,472
                                                                                                                --------------------
                                                  Total Common Collective Trusts                                     9,750,981
                                                                                                                --------------------

                                         MUTUAL FUNDS:
           Dodge and Cox                 Dodge and Cox Stock Fund                           35,072        **        5,382,138
   *       Putnam                        Putnam Voyager Fund                               189,093        **        3,581,426
           Artisan                       Artisan Mid Cap Fund                               85,369        **        2,600,333
   *       Putnam                        Putnam International Equity Fund                   40,737        **        1,284,858
           PIMCO                         PIMCO Total Return Fund                           104,241        **        1,082,018
           Dreyfus                       Dreyfus Mid-Cap Value Fund                         24,867        **          797,737
   *       Putnam                        Putnam Small Cap Growth Fund CL Y                  41,928        **          933,743
           UAM Trust Company             UAM/ICM Small Company Fund                         19,338        **          722,659
           Morgan Stanley                MSIF Institutional International Equity Fund       28,689        **          590,413
                                                                                                                --------------------
                                                  Total Mutual Funds                                               16,975,325
                                                                                                                --------------------

------------------------------------------------------------------------------------------------------------------------------------

See accompanying report of independent registered public accounting firm.




                                                           Page 18 of 22






                                                                                    U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES
                                                                                          EMPLOYER IDENTIFICATION NUMBER: 98-0047580
                                                                                                                    PLAN NUMBER: 007
                                                                                                        SCHEDULE H, PART IV, LINE 4I
                                                                                            SCHEDULE OF ASSETS (HELD AT END OF YEAR)
                                                                                                                           CONTINUED
                                                                                                                   DECEMBER 31, 2006
------------------------------------------------------------------------------------------------------------------------------------

  (a)                 (b)                                     (c)                                         d)            (e)
PARTY IN                                                                                   NUMBER OF                  CURRENT
INTEREST       IDENTITY OF ISSUER                   DESCRIPTION OF INVESTMENT                UNITS       COST          VALUE
--------   ---------------------------   ----------------------------------------------   -----------    ----   --------------------

                                                                                                   
                                         SYNTHETIC GUARANTEED INVESTMENT CONTRACTS:
           Monumental Life Insurance     Synthetic GIC, Dwight Managed Target
             Company                       2 F1 Cl B, no specified maturity date, 5.08%                   **      $ 1,981,755
           Monumental Life Insurance     Synthetic GIC, Dwight Managed Target
             Company                       5 F1 Cl B, no specified maturity date, 5.08%                   **        1,108,303
           Monumental Life Insurance     Synthetic GIC, Dwight Int Core Plus
             Company                       F1 Cl B, no specified maturity date, 5.08%                     **         423,125

           State Street Bank             Synthetic GIC, Dwight Managed Target
                                           2 F1 Cl B, no specified maturity date, 5.04%                   **        1,981,755
           State Street Bank             Synthetic GIC, Dwight Managed Target
                                           5 F1 Cl B, no specified maturity date, 5.04%                   **        1,108,303
           State Street Bank             Synthetic GIC, Dwight Int Core Plus
                                           F1 Cl B, no specified maturity date, 5.04%                     **          423,125
                                                                                                                --------------------
                                                  Total Synthetic Guaranteed
                                                    Investment Contracts                                            7,026,366
                                                                                                                --------------------

                                         COMMON STOCK:
   *       Rio Tinto plc ADRs            Common Stock                                       13,357        **        2,838,223
                                                                                                                --------------------

   *       Various participants          Participant loans (maturing 2007 to 2015
                                           at interest rates ranging from 5.0% to 10.0%)       499        **        2,611,022
                                                                                                                --------------------

                                                  Total Investments                                               $39,227,723
                                                                                                                ====================


* denotes a party-in-interest as defined by ERISA
** not required as investments are participant directed

------------------------------------------------------------------------------------------------------------------------------------
See accompanying report of independent registered public accounting firm.                                                         19



                                                           Page 19 of 22





                                    SIGNATURE
                                    ---------

         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
the trustees (or other persons who  administer  the employee  benefit plan) have
duly  caused this  annual  report to be signed on its behalf by the  undersigned
hereunto duly authorized.


                                U.S. BORAX INC. 401(k) PLAN FOR HOURLY EMPLOYEES



                                By:  /s/  Leah G. Cooper
                                   ------------------------------------------
                                   Name:  Leah G. Cooper
                                   Title: Vice President, Lease (RTM)

Date:  June 29, 2007



                                 Page 20 of 22


Exhibit        Description
-------        -----------

23.1           Consent of Tanner LC








                                 Page 21 of 22