SUPPLEMENTAL
      INDENTURE No. 5

    


    


    dated
      as
      of December 21, 2006 

    


    among

    


    CENTURY
      ALUMINUM COMPANY,

    as
      Issuer

    


    


    CENTURY
      CALIFORNIA LLC,

    as
      a
      Guarantor 

    


    and

    


    WILMINGTON
      TRUST COMPANY,

    as
      Trustee

    


    


    


    1.75%
      CONVERTIBLE SENIOR NOTES DUE AUGUST 1, 2024

    


    



    THIS
      SUPPLEMENTAL INDENTURE NO. 5 (this “Supplemental
      Indenture”),
      entered into as of December 21, 2006, is among Century Aluminum Company, a
      corporation duly organized under the laws of the State of Delaware (the
“Company”),
      Century California LLC, a limited liability organized under the laws of
      Delaware, as a Guarantor (the “Undersigned”)
      and
      Wilmington Trust Company, as trustee (the “Trustee”).

     

    RECITALS

     

    WHEREAS,
      the Company and the Trustee entered into the Indenture, dated as of August
      9,
      2004 (the “Original
      Indenture,”
as
      amended by Supplemental Indenture No. 1, dated as of October 26, 2004, between
      the Company and the Trustee, Supplemental Indenture No. 2, dated as of October
      26, 2004, among the Company, the Guarantors party thereto and the Trustee,
      Supplemental Indenture No. 3, dated as of July 25, 2005, among the Company,
      Century Aluminum of Kentucky LLC and the Trustee, Supplemental Indenture No.
      4,
      dated as of December 29, 2005, among the Company, NSA General Partnership and
      the Trustee, and as amended and supplemented by this Supplemental Indenture,
      hereinafter called the “Indenture”),
      relating to the Company’s 1.75% Convertible Senior Notes due August 1, 2024 (the
“Securities”);
      

    WHEREAS,
      the Company has agreed in Section 6.09 of the Indenture to cause certain of
      its
      Subsidiaries to provide Securities Guaranties in certain circumstances;
      and

    WHEREAS,
      the Undersigned is required pursuant to such Section 6.09 to execute and deliver
      this Supplemental Indenture to evidence its Securities Guaranty.

     

    AGREEMENT

     

    NOW,
      THEREFORE, in consideration of the premises and mutual covenants herein
      contained and intending to be legally bound, the parties to this Supplemental
      Indenture, hereby agree as follows:

     

    Section
      1. Capitalized terms used herein and not otherwise defined herein are used
      as
      defined in the Indenture.

     

    Section
      2. The Undersigned, by its execution of this Supplemental Indenture, agrees
      to
      be a Guarantor under the Indenture on the terms set forth below.

     

    Section
      3. Subject to the provisions in this Supplemental Indenture, the Guarantor
      hereby irrevocably and unconditionally guarantees, jointly and severally, on
      a
      senior unsecured basis, the full and punctual payment (or delivery, as the
      case
      may be), if and when due, of (i) the principal amount or interest due on any
      Security, whether on the Final Maturity Date, upon redemption or repurchase,
      or
      otherwise, (ii) the Make Whole Premium payable, if any, on any Security, and
      (iii) all other amounts payable by the Company under the Indenture (including,
      without limitation, the Company’s obligation to deliver Cash, Common Stock, or
      other securities, assets or property (including Cash) upon conversion of the
      Securities).  Upon
      failure by the Company to pay (or deliver, as the case may be) punctually any
      such amount if and when due, the Guarantor shall forthwith on demand pay (or
      deliver, as the case may be) the amount (or consideration) not so paid (or
      delivered) at the place and in the manner specified in the Indenture. To
      the
      extent that the Company has an election to deliver the form of payment, the
      Guarantor shall have the same right of election.

     

    Section
      4. The obligations of the Guarantor are unconditional and absolute and, without
      limiting the generality of the foregoing, will not be released, discharged
      or
      otherwise affected by

    (i)
       any
      extension, renewal, settlement, compromise, waiver or release in respect of
      any
      obligation of the Company under the Indenture or any Security, by operation
      of
      law or otherwise;

     

    (ii)
       any
      modification or amendment of or supplement to the Indenture or any
      Security;

     

    (iii)
       any
      change in the corporate existence, structure or ownership of the Company, or
      any
      insolvency, bankruptcy, reorganization or other similar proceeding affecting
      the
      Company or its assets or any resulting release or discharge of any obligation
      of
      the Company contained in the Indenture or any Security;

     

    (iv)
       the
      existence of any claim, set-off or other rights which the Guarantor may have
      at
      any time against the Company, the Trustee or any other Person, whether in
      connection with the Indenture or any unrelated transactions; provided
      that
      nothing herein prevents the assertion of any such claim by separate suit or
      compulsory counterclaim;

     

    (v)
       any
      invalidity or unenforceability relating to or against the Company for any reason
      of the Indenture or any Security, or any provision of applicable law or
      regulation purporting to prohibit the payment by the Company of the principal
      amount, Make Whole Premium, if any, or interest due on any Security or any
      other
      amount payable by the Company under the Indenture; or

     

    (vi)
       any
      other
      act or omission to act or delay of any kind by the Company, the Trustee or
      any
      other Person or any other circumstance whatsoever which might, but for the
      provisions of this paragraph, constitute a legal or equitable discharge of
      or
      defense to the Guarantor’s obligations hereunder.

     

    Section
      5. The Guarantor’s obligations under its Securities Guaranty will remain in full
      force and effect until the principal of, Make Whole Premium, if any, and
      interest on the Securities and all other amounts payable by the Company
      (including, without limitation, the Company’s obligation to deliver Cash, Common
      Stock, or other securities, assets or property (including Cash) upon conversion
      of the Securities) under the Indenture have been paid in full. If at any time
      any payment of the principal of, Make Whole Premium, if any, or interest on
      any
      Security or any other amount payable by the Company (including, without
      limitation, the Company’s obligation to deliver Cash, Common Stock, or other
      securities, assets or property (including Cash) upon conversion of the
      Securities) under the Indenture is rescinded or must be otherwise restored
      or
      returned upon the insolvency, bankruptcy or reorganization of the Company or
      otherwise, the Guarantor’s obligations hereunder with respect to such payment
      will be reinstated as though such payment had been due but not made at such
      time.

     

    Section
      6.  Each
      Guarantor irrevocably waives acceptance hereof, presentment, demand, protest
      and
      any notice not provided for herein, as well as any requirement that at any
      time
      any action be taken by any Person against the Company or any other
      Person.

     

    Section
      7. Upon making any payment with respect to any obligation of the Company
      pursuant to this Supplemental Indenture, the Guarantor making such payment
      will
      be subrogated to the rights of the payee against the Company with respect to
      such obligation; provided
      that the
      Guarantor may not enforce either any right of subrogation, or any right to
      receive payment in the nature of contribution, or otherwise, from any other
      Guarantor, with respect to such payment so long as any amount payable by the
      Company hereunder or under the Securities remains unpaid.

     

    Section
      8. If acceleration of the time for payment of any amount payable by the Company
      under the Indenture or the Securities is stayed upon the insolvency, bankruptcy
      or reorganization of the Company, all such amounts otherwise subject to
      acceleration under the terms of the Indenture are nonetheless payable by the
      Guarantor hereunder forthwith on demand by the Trustee or the
      Holders.

     

    Section
      9. Notwithstanding anything to the contrary in this Supplemental Indenture,
      the
      Guarantor, and by its acceptance of Securities, each Holder, hereby confirms
      that it is the intention of all such parties that the Securities Guaranty of
      such Guarantor not constitute a fraudulent conveyance under applicable
      fraudulent conveyance provisions of the United States Bankruptcy Code or any
      comparable provision of state law. To effectuate that intention, the Trustee,
      the Holders and the Guarantor hereby irrevocably agree that the obligations
      of
      the Guarantor under its Securities Guaranty are limited to the maximum amount
      that would not render the Guarantor’s obligations subject to avoidance under
      applicable fraudulent conveyance provisions of the United States Bankruptcy
      Code
      or any comparable provision of state law.

     

    Section
      10.  The
      execution by the Undersigned of this Supplemental Indenture evidences the
      Securities Guaranty of such Guarantor, whether or not the person signing as
      an
      officer of the Guarantor still holds that office at the time of authentication
      of any Security. The delivery of any Security by the Trustee after
      authentication constitutes due delivery of the Securities Guaranty set forth
      in
      the Indenture on behalf of the Guarantor.

     

    Section
      11. The Securities Guaranty of the Guarantor will terminate and be automatically
      released upon the release or discharge of the guarantee of the Senior Notes
      of
      such Guarantor as set forth in Section 6.09(b) of the Indenture.

     

    Section
      12. This Supplemental Indenture shall be governed by and construed in accordance
      with the laws of the State of New York.

     

    Section
      13. This Supplemental Indenture may be signed in various counterparts which
      together will constitute one and the same instrument.

     

    Section
      14.
      This
      Supplemental Indenture is an amendment supplemental to the Indenture and the
      Indenture and this Supplemental Indenture will henceforth be read
      together.

     

    Section
      15. The recitals contained in this Supplemental Indenture shall be taken as
      the
      statements of the Company and the Guarantors, and the Trustee assumes no
      responsibility for their correctness. The Trustee makes no representations
      as to
      the validity or sufficiency of this Supplemental Indenture.


    
      
         

      

      
         

        
          

        

      

      
         

      

    


    IN
      WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture
      to
      be duly executed as of the date first above written.

     

    

      


      
        	
                CENTURY
                  ALUMINUM COMPANY, as Issuer

                 

              
	
                By:

              	
                /s/
                  Michael Bless

              
	 	
                Name:
                   Michael
                  Bless

              
	 	
                Title: Chief
                  Financial Officer

              


      

      


      


      
        	
                WILMINGTON
                  TRUST COMPANY, as Trustee

                 

              
	
                By:

              	
                /s/
                  Kristin L. Moore

              
	 	
                Name: Kristin
                  L. Moore

              
	 	
                Title: Senior
                  Financial
                  Services Officer

              


      

      


      


      
        	
                CENTURY
                  CALIFORNIA LLC, as a Guarantor

                By
                  Century Kentucky, Inc., Manager

                 

              
	
                By:

              	
                /s/
                  Peter C. McGuire

              
	 	
                Name: Peter
                  C. McGuire

              
	 	
                Title: Vice
                  President