Exhibit 4.21 Supplemental Indenture No. 3 - 7.5% Senior Notes


     

    SUPPLEMENTAL
      INDENTURE No. 3

     

    dated
      as
      of December 21, 2006

     

    among

     

    CENTURY
      ALUMINUM COMPANY, 

    as
      Issuer

    


    


    CENTURY
      CALIFORNIA LLC

    as
      a
      Guarantor 

    


    and

    


    WILMINGTON
      TRUST COMPANY,

    as
      Trustee

    


    ________________________

    


    


    71/2%
      SENIOR NOTES DUE 2014

    



    
      
         

      

      
         

        
          

        

      

      
         

      

    


    


    THIS
      SUPPLEMENTAL INDENTURE NO. 3 (this “Supplemental
      Indenture”),
      entered into as of December 21, 2006, among Century Aluminum Company, a Delaware
      corporation (the “Company”),
      Century
      California LLC, a Delaware limited liability company, as a Guarantor
(the
      “Undersigned”)
      and
      Wilmington Trust Company, as trustee (the “Trustee”).

     

    RECITALS

     

    WHEREAS,
      the Company, the Guarantors party thereto and the Trustee entered into the
      Indenture, dated as of August 26, 2004 (the "Indenture"),
      relating to the Company’s 71/2%
      Senior
      Notes due 2014 (the "Notes"),
      as
      amended by Supplemental Indenture No. 1, dated
      as
      of July 25, 2005, among the Company, Century Aluminum of Kentucky LLC and the
      Trustee, and Supplemental Indenture No. 2, dated as of December 29, 2005, among
      the Company, NSA General Partnership and the Trustee; and

     

    WHEREAS,
      as a condition to the Trustee entering into the Indenture and the purchase
      of
      the Notes by the Holders, the Company agreed pursuant to the Indenture to cause
      any newly acquired or created Domestic Restricted Subsidiaries (other than
      Foreign-Owned Parent Holding Companies) to provide Guaranties.

     

    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 and to be bound by the terms of the Indenture
      applicable to Guarantors, including, but not limited to, Article 10
      thereof.

     

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

     

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

     

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

     

    Section
      6. The
      Trustee makes no representation as to the validity or adequacy of this
      Supplemental Indenture or the recitals contained herein.

     

     


    
      
         

      

      
         

        
          

        

      

      
         

      

    


    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

            


    

    


    


    
      	
              CENTURY
                CALIFORNIA LLC, as a Guarantor

              By
                Century Kentucky, Inc., Manager

               

            
	
              By:

            	
              /s/
                Peter C. McGuire

            
	 	
              Name: Peter
                C. McGuire

            
	 	
              Title: Vice
                President

            


    

    


    


    
      	
              WILMINGTON
                TRUST COMPANY, as Trustee

               

            
	
              By:

            	
              /s/
                Kristin L. Moore

            
	 	
              Name: Kristin
                L. Moore

            
	 	
              Title: Senior
                Financial
                Services Officer