Document:

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                                                                     Exhibit 4.6

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                          PLEDGE AND SECURITY AGREEMENT

                                   dated as of

                                  April 2, 2001

                                      among

                            CENTURY ALUMINUM COMPANY,
                         the other Pledgors party hereto

                                       and

                            WILMINGTON TRUST COMPANY,
                           as Collateral Agent for the
              Trustee and the Holders of Century Aluminum Company's
               11-3/4 Senior Secured First Mortgage Notes due 2008

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                                TABLE OF CONTENTS

                                                                     PAGE
   SECTION 1.  Defined Terms...........................................2
   SECTION 2.  Pledge and Grant of Security Interest...................3
   SECTION 3.  Security for Obligation.................................4
   SECTION 4.  Maintaining the Cash Collateral Account.................4
   SECTION 5.  Delivery of Collateral..................................5
   SECTION 6.  Liquid Investments......................................6
   SECTION 7.  Representations and Warranties..........................7
   SECTION 8.  Further Assurances......................................8
   SECTION 9.  Covenants...............................................9
   SECTION 10.  Power of Attorney.....................................10
   SECTION 11.  No Assumption of Duties; Reasonable Care..............11
   SECTION 12.  Indemnity.............................................12
   SECTION 13.  Remedies upon Event of Default........................12
   SECTION 14.  Expenses..............................................14
   SECTION 15.  Security Interest Absolute............................14
   SECTION 16.  Continuing Security Interest; Termination.............15
   SECTION 17.  Additional Pledgors...................................15
   SECTION 18.  Successors and Assigns................................16
   SECTION 19.  Miscellaneous Provisions..............................16

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         This COLLATERAL PLEDGE AND SECURITY AGREEMENT (this "PLEDGE AGREEMENT")
is made and entered into as of April 2, 2001 by Century Aluminum Company, a
Delaware corporation (with its successors, the "COMPANY"), the Guarantors listed
on the signature pages hereof (each, together with its successors, a "PLEDGOR"
and, collectively with the Company and any other Person that becomes a Pledgor
hereunder from time to time pursuant to Section 17, the "PLEDGORS"), in favor of
Wilmington Trust Company, a Delaware banking corporation, as trustee (the
"TRUSTEE") under the Indenture referred to herein, in its capacity as collateral
agent (the "COLLATERAL AGENT") for the Trustee and the holders from time to time
(the "HOLDERS") of the Notes (as defined herein), issued by the Company under
the Indenture referred to below.

                                   WITNESSETH

          WHEREAS, the Pledgors and the Trustee have entered into that certain
indenture dated as of the date hereof (as amended, restated, supplemented or
otherwise modified from time to time, the "INDENTURE"), pursuant to which the
Company is issuing $325,000,000 in aggregate principal amount of 11-3/4% Senior
Secured First Mortgage Notes due 2008 (the "NOTES") on the date hereof;

         WHEREAS, the Pledgors have established an account (the "CASH COLLATERAL
ACCOUNT") with Wilmington Trust FSB, at its office at 520 Madison Avenue, New
York, New York, Account No. 54772-0, in the name of "Wilmington Trust Company,
as Collateral Agent for the benefit of the trustee and holders of the 11-3/4%
Senior Secured First Mortgage Notes Due 2008 of Century Aluminum Company
Collateral Pledge Account";

         WHEREAS, pursuant to the Indenture and the other Security Documents,
the Pledgors are required to deposit into the Cash Collateral Account various
amounts, including cash proceeds from the sale, lease, transfer, or other
disposition, or series of related sales, leases, transfers or other
dispositions, of Restricted Assets having an aggregate fair market value (as
determined under the Indenture) of $2.5 million or more, and, subject to
specified exceptions, any Casualty Proceeds of $2.5 million or more
(collectively, the "CASH PROCEEDS");

         WHEREAS, to secure the payment and performance of all of its Secured
Obligations (as defined herein), the Pledgors have agreed (i) to pledge to the
Collateral Agent for the benefit of the Secured Parties (as defined herein), a
security interest in the Collateral (as defined herein) and (ii) to execute and
deliver this Pledge Agreement; and

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         WHEREAS, it is a condition precedent to the initial purchase of the
Notes by the initial Holders thereof that each Pledgor shall have granted the
security interest and made the pledge contemplated by this Pledge Agreement.

         NOW, THEREFORE, in consideration of the mutual promises herein
contained, and in order to induce the initial Holders of the Notes to purchase
the Notes, each Pledgor hereby agrees with the Collateral Agent for the benefit
of the Secured Parties, as follows:

         SECTION 1. Defined Terms.(a) Capitalized terms used and not defined in
this Pledge Agreement have the meanings set forth or referred to in the
Indenture.

         (b) Unless otherwise defined herein or in the Indenture, terms used in
the UCC (as defined below) and/or in the Federal Book Entry Regulations (as
defined below) are used in this Pledge Agreement as such terms are defined in
the UCC and/or the Federal Book Entry Regulations.

         (c) The following terms used herein have the meanings set forth below:

         "CASH COLLATERAL ACCOUNT" has the meaning assigned to such term in the
recitals.

         "CASH PROCEEDS" has the meaning assigned to such term in the recitals.

         "COLLATERAL" has the meaning assigned to such term in Section.

         "FEDERAL BOOK ENTRY REGULATIONS" means the federal regulations
contained in Subpart B governing book-entry securities consisting of U.S.
Treasury bills, notes and bonds and Subpart D of 31 C.F.R. Part 357, 31 C.F.R.
Section 357.2, Section 357.10 through Section 357.14 and Section 357.41 through
Section 357.44.

         "INDENTURE" has the meaning assigned to such term in the recitals.

         "LIQUID INVESTMENTS" means (i) United States Treasury bills, notes or
bonds held in TRADES (or any security entitlement with respect thereto) that
mature within six months of their date of acquisition hereunder and (ii)
money-market funds, at least 95% of the assets of which are U.S. Government
Obligations (or any security entitlement with respect thereto), in each case
held by the Collateral Agent in the manner required by Section.

         "NOTES" has the meaning assigned to such term in the recitals.

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         "POST-DEFAULT RATE" means the interest rate owed on any overdue
payments of principal or interest on the Notes as provided in each Note.

         "SECURED OBLIGATIONS" means (a) in the case of the Company, (i) all
Obligations under the Notes, (ii) all other amounts now or hereafter payable by
the Company hereunder or under the Indenture or any other Security Document,
(iii) all other obligations, liabilities, covenants and duties of the Company
hereunder and the Indenture or any other Security Document, (b) in the case of
each Pledgor other than the Company, the Obligations of such Pledgor under its
Note Guaranty and (c) in the case of each Pledgor, any amendments, restatements,
renewals, extensions or modifications of any of the foregoing.

         "SECURED PARTIES" means the Collateral Agent, the Trustee and the
Holders.

         "SECURITY INTERESTS" means the security interests in the Collateral
granted hereunder securing the Secured Obligations.

         "UCC" means the Uniform Commercial Code as in effect in the State of
New York; provided that if by reason of mandatory provisions of law, the
perfection or the effect of perfection or non-perfection of the Security
Interest in any Collateral is governed by the Uniform Commercial Code as in
effect in a jurisdiction other than New York, "UCC" means the Uniform Commercial
Code as in effect in such other jurisdictions for purposes of the provisions
hereof relating to such perfection or effect of perfection or non-perfection.

          SECTION 2. Pledge and Grant of Security Interest. Each Pledgor hereby
pledges to the Collateral Agent for the benefit of the Secured Parties, and
hereby grants to the Collateral Agent for the benefit of the Secured Parties, a
continuing security interest in and to all of such Pledgor's right, title and
interest in and to all of the following, whether now owned or hereafter acquired
by such Pledgor, wherever located and whether now or hereafter existing or
arising (hereinafter collectively referred to as the "COLLATERAL"), whether
characterized as investment property, general intangibles or otherwise:

         (a) the Cash Collateral Account;

         (b) all cash, monies, investment property, instruments and financial
assets (including without limitation, the Liquid Investments) held in the Cash
Collateral Account;

         (c) all Cash Proceeds, whether or not held in the Cash Collateral
Account;

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         (d) all dividends, interest, cash, monies and other property from time
to time received, receivable or otherwise distributed or distributable in
respect of, or in exchange for, any or all such Collateral; and

         (e) all proceeds of any of the foregoing clauses (a) through (d).

         SECTION 3. Security for Obligation. This Pledge Agreement and the
grant of a security interest in the Collateral hereunder secures the prompt and
complete payment and performance by each Pledgor of such Pledgor's Secured
Obligations.

         SECTION 4. Maintaining the Cash Collateral Account. So long as any
Secured Obligation shall remain outstanding:

         (a) Prior to or concurrently with the execution and delivery hereof,
the Collateral Agent shall establish the Cash Collateral Account on its books as
a separate account segregated from all other custodial or collateral accounts at
its office at Wilmington Trust FSB, 520 Madison Avenue, New York, New York,
10022, Attention: Corporate Trustee Department. The Company and the Collateral
Agent will maintain the Cash Collateral Account as a securities account with
Wilmington Trust FSB in the State of New York.

         (b) Except as otherwise provided by the provisions of Section 13 and
Section 16, no amount shall be paid or released to or for the account of, or
withdrawn by or for the account of, any Pledgor or any other Person from the
Cash Collateral Account.

         (c) The Cash Collateral Account shall be subject to such applicable
laws, and such applicable regulations of the Board of Governors of the Federal
Reserve System and of any other appropriate banking or governmental authority,
as may now or hereafter be in effect.

         (d) Subject to the other terms and conditions of this Pledge Agreement,
all funds or other property held by the Collateral Agent pursuant to this Pledge
Agreement shall be held in the Cash Collateral Account subject to the exclusive
dominion and control of the Collateral Agent and exclusively for the ratable
benefit of the Secured Parties and, to the extent required by applicable law to
ensure perfection of the Security Interest on a first priority basis, segregated
from all other funds or other property otherwise held by the Collateral Agent.

         (e) Nothing contained in this Pledge Agreement shall (i) afford any
Pledgor any right to issue entitlement orders with respect to any of the
security entitlements constituting Collateral or any securities account in which
any such

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security entitlement may be carried, or otherwise afford any Pledgor control of
any such security entitlement or securities account or (ii) otherwise give rise
to any rights of Pledgor with respect to such security entitlements or any
securities account in which any such security entitlement may be carried, other
than each Pledgor's rights under this Pledge Agreement as the beneficial owner
of Collateral pledged to and subject to the exclusive dominion and control of
the Collateral Agent in its capacity as such (and not as a securities
intermediary). Each Pledgor acknowledges, confirms and agrees that the
Collateral Agent is an entitlement holder of the Collateral solely as Collateral
Agent and not as a securities intermediary.

         SECTION 5. Delivery of Collateral. All Cash Proceeds or other amounts
required to be delivered to the Collateral Agent pursuant to the Indenture
(including without limitation Section 11.03 thereof) or any Security Document,
including this Pledge Agreement, shall be deposited in the Cash Collateral
Account.

         (b) All cash, certificates or instruments representing or evidencing
the Collateral shall be delivered to and held by or on behalf of the Collateral
Agent in the State of New York pursuant hereto and shall be in suitable form for
transfer by delivery, or shall be accompanied by duly executed instruments of
transfer or assignment in blank, all in form and substance satisfactory to the
Collateral Agent. The Collateral Agent shall have the right, at any time in its
discretion and without notice to any Pledgor, to transfer to or to register in
the name of the Collateral Agent or any of its nominees any or all of the
Collateral. In addition, the Collateral Agent shall have the right at any time
to exchange certificates or instruments representing or evidencing any or all of
the Collateral for certificates or instruments of smaller or larger
denominations. Also, the Collateral Agent shall have the right at any time to
convert Collateral consisting of financial assets credited to the Cash
Collateral Account to Collateral consisting of financial assets held directly by
the Collateral Agent, and to convert Collateral consisting of financial assets
held directly by the Collateral Agent to Collateral consisting of financial
assets credited to the Cash Collateral Account.

         (c) With respect to any Collateral in which any Pledgor has any right,
title or interest and that constitutes an uncertificated security, such Pledgor
shall cause the issuer thereof to register the Collateral Agent as the
registered owner of such security.

         (d) With respect to any Collateral in which any Pledgor has any right,
title or interest and that constitutes a security entitlement, such Pledgor
shall cause the securities intermediary with respect to such security
entitlement to identify in

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its records the Collateral Agent as the entitlement holder of such security
entitlement against such securities intermediary.

         (e) With respect to any Collateral that constitutes a securities
account, each Pledgor will comply with Section with respect to all security
entitlements carried in such securities account.

         (f) Upon transfer of any financial assets to the Cash Collateral
Account, the Collateral Agent shall make appropriate book entries indicating
that such assets have been credited to the Cash Collateral Account.

         (g) Any income received by the Collateral Agent with respect to the
balance from time to time standing to the credit of the Cash Collateral Account,
including any interest or capital gains on Liquid Investments, shall remain, or
be deposited, in the Cash Collateral Account. All right, title and interest in
and to the cash amounts on deposit from time to time in the Collateral Account
together with any Liquid Investments from time to time made pursuant to Section
hereof shall vest in the Collateral Agent, shall constitute part of the
Collateral hereunder and shall not constitute payment of the Secured Obligations
until applied thereto as hereinafter provided.

         (h) Concurrently with the execution and delivery of this Pledge
Agreement, the Collateral Agent shall deliver a certificate of an officer of the
Collateral Agent, confirming the Collateral Agent's establishment and separate
maintenance of the Cash Collateral Account, all in accordance with this Pledge
Agreement.

         SECTION 6. Liquid Investments. Amounts on deposit in the Collateral
Account shall be invested and re-invested from time to time in Liquid
Investments pursuant to Section, which Liquid Investments shall be held in the
name and be under the control of the Collateral Agent pursuant to the provisions
of Section, provided that, if an Event of Default has occurred and is
continuing, the Collateral Agent shall, if instructed by the Trustee, liquidate
any such Liquid Investments and apply or cause to be applied the proceeds
thereof to the payment of the Secured Obligations in the manner specified in
Section.

         (b) Not later than three Business Day after any receipt by the
Collateral Agent of cash (whether Cash Proceeds or as proceeds of any Liquid
Investments or other Collateral) for deposit in the Cash Collateral Account, the
Collateral Agent shall invest such funds in the Wilmington U.S. Government
Portfolio/Service Class Shares; provided that, if, prior to the time of such
investment, the Collateral Agent receives an Officers' Certificate from the
Company specifying an alternative Liquid Investment, the Collateral Agent shall

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invest such cash in the specified Liquid Investment promptly, but in any event
within two Business Days after receipt of such notice.

         SECTION 7. Representations and Warranties. Each Pledgor, jointly and
severally, hereby represents and warrants that:

         (a) The execution and delivery by each Pledgor of, and the performance
by such Pledgor of its obligations under, this Pledge Agreement will not (1)
contravene (A) any provision of applicable law, (B) the certificate of
incorporation or by-laws (or other organizational documents in the case of any
non-corporate Pledgor) of any Pledgor, (C) any agreement or other instrument
binding upon any Pledgor or any of its subsidiaries or (D) any judgment, order
or decree of any governmental body, agency or court having jurisdiction over the
Company or any of its subsidiaries, except, in the case of (C) and (D), for
contraventions that would not have a material adverse effect on the Company and
its subsidiaries taken as a whole or the Security Interest in the Collateral or
(2) result in the creation or imposition of any Lien on any assets of any
Pledgor, except for the security interests granted under this Pledge Agreement.

         (b) No consent, approval, authorization, order of, action by notice to,
filing or qualification with, any governmental authority, regulatory body,
agency or other Person is required for (i) the execution, delivery or
performance by any Pledgor of its obligations under this Pledge Agreement, (ii)
the grant by any Pledgor of the Security Interest, (iii) the perfection or
maintenance of the Security Interest (including the first priority nature of
such Security Interest) or (iv) the exercise by the Collateral Agent of its
voting or other rights provided for in this Pledge Agreement or the remedies in
respect of the Collateral pursuant to this Pledge Agreement, except as may be
required in connection with the disposition of any portion of the Collateral by
laws affecting the offering and sale of securities generally.

         (c) Each Pledgor is the beneficial owner of the Collateral pledged by
it hereunder, free and clear of any Lien, claim, option or right of any Person
(except for the Security Interests and any Permitted Encumbrances). No financing
statement or instrument similar in effect covering all or any part of such
Collateral is on file in any public or recording office, other than any
financing statements filed from time to time pursuant to this Pledge Agreement
and the other Security Documents.

         (d) This Pledge Agreement has been duly authorized, validly executed
and delivered by each Pledgor and constitutes a valid and binding agreement of
such Pledgor, enforceable against such Pledgor in accordance with its terms,
except as (i) the enforceability hereof may be limited by bankruptcy, insolvency

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or similar laws now or hereafter in effect relating to or affecting creditors'
rights or remedies generally (regardless of whether considered in an action at
law or in equity) and (ii) the availability of equitable remedies may be limited
by equitable principles of general applicability.

         (e) Assuming compliance by the Collateral Agent with its agreements
hereunder, the pledge and grant by each Pledgor of a Security Interest in the
Collateral pursuant to this Pledge Agreement for the ratable benefit of the
Secured Parties will constitute a valid and perfected first-priority security
interest in such Collateral, securing the payment of the Secured Obligations of
such Pledgor, enforceable as such against all creditors of such Pledgor (and any
persons purporting to purchase any of the Collateral from such Pledgor), subject
to no other Liens other than Permitted Encumbrances.

         (f) There are no legal or governmental proceedings pending or, to each
Pledgor's knowledge, threatened to which the Company or any of its subsidiaries
is a party or to which any of the properties of the Company or any such
subsidiary is subject that would materially adversely affect the power
(corporate or otherwise) or ability of any Pledgor to perform its obligations
under this Pledge Agreement or to consummate the transactions contemplated
hereby.

         (g) The pledge of the Collateral pursuant to this Pledge Agreement is
not prohibited by law or governmental regulation (including, without limitation,
Regulations G, T, U and X of the Board of Governors of the Federal Reserve
System) applicable to any Pledgor.

         (h) No Event of Default has occurred and is continuing.

         (i) The jurisdiction (for purposes of Section 8-110(e) of the UCC and
31 CFR Section 357.11(b))) of the securities intermediary that maintains the
Cash Collateral Account and all securities accounts carrying the Collateral is
New York.

         SECTION 8. Further Assurances. Each Pledgor agrees that from time to
time, at its own expense, such Pledgor will promptly execute and deliver all
further instruments and documents, and take all further action, that may be
necessary or required by applicable law or that the Collateral Agent may
reasonably request, in order to perfect and protect the Security Interest
granted or purported to be granted hereby or to enable the Collateral Agent to
exercise and enforce its rights and remedies hereunder with respect to any
Collateral. Without limiting the generality of the foregoing, each Pledgor will:
(i) if any Collateral shall be evidenced by a promissory note or other
instrument, deliver and pledge to the Collateral Agent hereunder such note or
instrument, duly indorsed and accompanied by duly executed instruments of
transfer or assignment, all in form

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and substance satisfactory to the Collateral Agent; (ii) execute and file such
financing or continuation statements, or amendments thereto, and such other
instruments or notices, as may be necessary or required by applicable law or as
the Collateral Agent may reasonably request, in order to perfect and preserve
the Security Interest granted or purported to be granted hereby; (iii) deliver
and pledge to the Collateral Agent for the benefit of the Secured Parties
certificates representing Collateral that constitutes certificated securities,
accompanied by undated stock or bond powers executed in blank; and (iv) deliver
to the Collateral Agent evidence that all other action that the Collateral Agent
may deem reasonably necessary or desirable in order to perfect and protect the
security interest created by Pledgor under this Pledge Agreement has been taken.

         (b) Each Pledgor hereby authorizes the Collateral Agent to file one or
more financing or continuation statements, and amendments thereto, relating to
all or any part of the Collateral without the signature of such Pledgor where
permitted by law. The Collateral Agent shall notify the applicable Pledgor of
the filing of any such financing statement and provide a copy to such Pledgor
upon filing. A photocopy or other reproduction of this Pledge Agreement or any
financing statement covering the Collateral or any part thereof shall be
sufficient as a financing statement where permitted by law.

         (c) Each Pledgor will furnish to the Collateral Agent from time to time
statements and schedules further identifying and describing the Collateral and
such other reports in connection with the Collateral as the Collateral Agent may
reasonably request, all in reasonable detail.

         (d) The Company will promptly pay all reasonable costs incurred in
connection with any of the foregoing within 30 days of receipt of an invoice
therefor. Each Pledgor also agrees, whether or not requested by the Collateral
Agent, to take all actions that are necessary to perfect or continue the
perfection of, or to protect the first priority of, the Collateral Agent's
Security Interest in and to the Collateral, including the filing of all
necessary financing and continuation statements, and to protect the Collateral
against the rights, claims or interests of third persons (other than any such
rights, claims or interests created by or arising through the Collateral Agent).

         SECTION 9. Covenants. Each Pledgor covenants and agrees with the
Collateral Agent for the benefit of the Secured Parties that, from and after the
date of this Pledge Agreement until the payment in full in cash of all
Obligations due and owing under the Indenture and the Notes, it will not:

         (i) sell or otherwise dispose of, and will not purport to sell or
otherwise dispose of, or grant any option or warrant with respect to, any of

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\the Collateral or its beneficial interest therein, except for any disposition
permitted by Section 11.02 and Section 11.03 of the Indenture;

                  (ii) create or permit to exist any Lien or other adverse
         interest in or with respect to its beneficial interest in any of the
         Collateral (except for the Security Interests and any Permitted
         Encumbrance);

                  (iii) enter into any agreement or understanding that restricts
         or inhibits or purports to restrict or inhibit the Collateral Agent's
         rights or remedies hereunder, including, without limitation, the
         Collateral Agent's right to sell or otherwise dispose of the
         Collateral; or

                  (iv) fail to pay or discharge any tax, assessment or levy of
         any nature with respect to its beneficial interest in the Collateral
         not later than five days prior to the date of any proposed sale under
         any judgment, writ or warrant of attachment with respect to such
         beneficial interest.

         SECTION 10. Power of Attorney. Each Pledgor hereby appoints and
constitutes the Collateral Agent as such Pledgor's attorney-in-fact (with full
power of substitution), with full authority in the place and stead of such
Pledgor and in the name of such Pledgor or otherwise, from time to time in the
Collateral Agent's discretion to take any action and to execute any instrument
that is necessary or advisable or as the Collateral Agent may deem necessary or
advisable to accomplish the purposes of this Pledge Agreement, including,
without limitation:

         (a) to ask for, demand, collect, sue for, recover, compromise, receive
and give acquittance and receipts for moneys due and to become due under or in
respect of any of the Collateral,

         (b) to receive, indorse and collect any drafts or other instruments,
documents and chattel paper, in connection with clause (a) above,

         (c) to file any claims or take any action or institute any proceedings
that the Collateral Agent may deem necessary or desirable for the collection of
any of the Collateral or otherwise to enforce the rights of the Collateral Agent
with respect to any of the Collateral, and

         (d) to pay or discharge taxes or Liens levied or placed upon the
Collateral that such Pledgor has failed to pay or discharge in accordance
herewith, the legality or validity thereof and the amounts necessary to
discharge the same to be determined by the Collateral Agent in its sole
reasonable discretion, and such payments made by the Collateral Agent to become
part of the Secured Obligations

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of such Pledgor to the Collateral Agent, due and payable immediately upon
demand;

provided, however, that the Collateral Agent shall have no obligation to perform
any of the foregoing actions. The Collateral Agent's authority under this
Section shall include, without limitation, the authority to indorse and
negotiate any checks or instruments representing proceeds of Collateral in the
name of such Pledgor, execute and give receipt for any certificate of ownership
or any document constituting Collateral, transfer title to any item of
Collateral, sign such Pledgor's name on all financing statements (to the extent
permitted by applicable law) or any other documents deemed necessary or
appropriate by the Collateral Agent to preserve, protect or perfect the security
interest in the Collateral and to file the same, prepare, file and sign such
Pledgor's name on any notice of Lien, and to take any other actions arising from
or incident to the powers granted to the Collateral Agent in this Pledge
Agreement. This power of attorney is coupled with an interest and is irrevocable
by the Pledgors.

         SECTION 11. No Assumption of Duties; Reasonable Care. The rights
and powers conferred on the Collateral Agent hereunder are solely to preserve
and protect the Security Interest of the Secured Parties in and to the
Collateral granted hereby and shall not be interpreted to, and shall not impose
any duties on the Collateral Agent in connection therewith other than those
expressly provided herein or imposed under applicable law. Except as provided by
applicable law or by the Indenture, the Collateral Agent shall be deemed to have
exercised reasonable care in the custody and preservation of the Collateral in
its possession if the Collateral is accorded treatment substantially equal to
that which the Collateral Agent accords similar property held by the Collateral
Agent for its own account, it being understood that the Collateral Agent in its
capacity as such shall not have any responsibility for (a) ascertaining or
taking action with respect to calls, conversions, exchanges, maturities or other
matters relative to any Collateral, whether or not the Collateral Agent has or
is deemed to have knowledge of such matters, (b) taking any necessary steps to
preserve rights against any parties with respect to any Collateral or (c)
investing or reinvesting any of the Collateral or any loss on any investment.
The Collateral Agent shall not be responsible for the sufficiency of the
Collateral or this Pledge Agreement and shall be entitled to all the rights,
benefits, privileges and immunities accorded to the Trustee under Article 7 of
the Indenture.

         SECTION 12. Indemnity. Each Pledgor, jointly and severally, shall
indemnify, hold harmless and defend the Collateral Agent and its directors,
officers, agents and employees, from and against, and shall pay on demand any
and all claims, actions, obligations, losses, liabilities and expenses,
including reasonable defense costs, reasonable investigative fees and costs, and
reasonable

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legal fees, costs and damages arising from the Collateral Agent's performance as
Collateral Agent under this Pledge Agreement, except to the extent that such
claim, action, obligation, loss, liability or expense is found in a final,
non-appealable judgment by a court of competent jurisdiction to have resulted
from such indemnified person's negligence or willful misconduct. This
indemnification shall survive the termination of this Pledge Agreement.

         SECTION 13. Remedies upon Event of Default. If any Event of Default
shall have occurred and be continuing:

         (a) The Collateral Agent and the other Secured Parties may exercise, in
addition to all other rights and remedies given by law or by this Pledge
Agreement or the Indenture, all of the rights and remedies with respect to the
Collateral of a secured party under the UCC (whether or not the UCC applies to
the affected Collateral) and also may require the Pledgors to, and each Pledgor
hereby agrees that it will at its expense and upon request of the Collateral
Agent forthwith, assemble all or part of the Collateral as directed by the
Collateral Agent and make it available to the Collateral Agent at a place and
time to be designated by the Collateral Agent that is reasonably convenient to
both parties and (ii) without notice except as specified below, sell the
Collateral or any part thereof in one or more parcels at any broker's board or
at public or private sale, in one or more sales or lots, at any of the
Collateral Agent's offices or elsewhere, for cash, on credit or for future
delivery, and upon such other terms as the Collateral Agent may deem
commercially reasonable. Each Pledgor agrees that, to the extent notice of sale
shall be required by law, at least ten days' notice to such Pledgor of the time
and place of any public sale or the time after which any private sale is to be
made shall constitute reasonable notification. The Collateral Agent shall not be
obligated to make any sale of Collateral regardless of notice of sale having
been given, the Collateral Agent may adjourn any public or private sale from
time to time by announcement at the time and place fixed therefor, and such sale
may, without further notice, be made at the time and place to which it was so
adjourned. The purchaser of any or all Collateral so sold shall thereafter hold
the same absolutely, free from any claim, encumbrance or right of any kind
whatsoever created by or through such Pledgor. Any sale of the Collateral
conducted in conformity with reasonable commercial practices of banks, insurance
companies, commercial-finance companies, or other financial institutions
disposing of property similar to the Collateral shall be deemed to be
commercially reasonable. The Collateral Agent and the other Secured Parties may,
in their own name or in the name of a designee or nominee, buy any of the
Collateral at any public sale and, if permitted by applicable law, at any
private sale. All expenses (including court costs and reasonable attorneys'
fees, expenses and disbursements) of, or incident to, the enforcement of any of
the provisions

                                       12
<PAGE>   15
hereof shall be recoverable from the proceeds of the sale or other disposition
of the Collateral.

         (b) The proceeds of any sale of, or other realization upon, all or any
part of the Collateral pursuant to this Section and any cash held in the Cash
Collateral Account at such time shall be applied by the Collateral Agent in the
following order of priorities:

                  (i) First: to the payment of all expenses of such sale,
         including compensation of the Collateral Agent or such other Person
         conducting such sale, and attorneys' fees and expenses incurred by such
         Person, together with interest on any such expenses paid by such Person
         at the Post-Default Rate from the date paid by such Person through the
         date repaid to such Person;

                  (ii) Second: to the payment of the expenses and other amounts
         payable under Section ; and

                  (iii) Third: to the Trustee to be held, applied and disbursed
         in accordance with Section 6.10 of the Indenture.

         (c) The Collateral Agent may, without notice to the Pledgors except as
required by law and at any time or from time to time, charge, set-off and
otherwise apply all or any part of the Secured Obligations against the Cash
Collateral Account or any part thereof.

         (d) Each Pledgor further agrees to use its reasonable best efforts to
do or cause to be done all such other acts as may be necessary to make any
disposition any portion of the Collateral pursuant to this Section valid and
binding and in compliance with any and all other applicable requirements of law.
Each Pledgor further agrees that a breach of any of the covenants contained in
this Section will cause irreparable injury to the Collateral Agent and the other
Secured Parties, that the Collateral Agent and the other Secured Parties have no
adequate remedy at law in respect of such breach and, as a consequence, that
each and every covenant contained in this Section shall be specifically
enforceable against each Pledgor, and, to the extent permitted by law, each
Pledgor hereby waives and agrees not to assert any defenses against an action
for specific performance of such covenants, except for a defense that no Event
of Default has occurred and is continuing.

         (e) Each Pledgor acknowledges the impossibility of ascertaining the
amount of damages that would be suffered by the Collateral Agent and the other
Secured Parties by reason of the failure by such Pledgor to perform any of the

                                    13
<PAGE>   16
covenants contained in this Section 13 and, consequently, agrees that, if such
Pledgor shall fail to perform any of such covenants, it will pay, as liquidated
damages and not as a penalty, an amount equal to the value of the Collateral on
the date the Collateral Agent shall demand compliance with this Section 13.

         SECTION 14. Expenses. Each Pledgor, jointly and severally, agrees that
it will, upon demand, pay to the Collateral Agent the amount of any and all
reasonable and duly documented expenses, including, without limitation, the
reasonable fees, expenses and disbursements of counsel, experts and agents
retained by the Collateral Agent, that the Collateral Agent may incur in
connection with (a) the administration of this Pledge Agreement, (b) the custody
or preservation of, or the sale of, collection from, or other realization upon,
any of the Collateral, (c) the exercise or enforcement of any of the rights of
the Collateral Agent or the other Secured Parties hereunder and (d) the failure
by any Pledgor to perform or observe any of the provisions hereof.

         SECTION 15. Security Interest Absolute. All rights of the Collateral
Agent and the other Secured Parties and the pledges, assignments and security
interests hereunder, and all obligations of the Pledgors hereunder, shall be
irrevocable, absolute and unconditional irrespective of and each Pledgor hereby
irrevocably waives (to the maximum extent permitted by applicable law) any
defenses it may now have or may hereafter acquire in any way relating to, any or
all of the following:

         (a) any lack of validity or enforceability of the Indenture or Notes or
any other agreement or instrument relating thereto;

         (b) any change in the time, manner or place of payment of, or in any
other term of, all or any of the Secured Obligations, or any other amendment or
waiver of or any consent to any departure from the Indenture or Notes or any
other agreement or instrument relating thereto;

         (c) any taking, exchange, surrender, release or non-perfection of any
Liens on any Collateral or any other collateral for all or any of the Secured
Obligations;

         (d) any manner of application of any Collateral or any other
collateral, or proceeds thereof, to all or any of the Secured Obligations, or
any manner of sale or other disposition of any Collateral or any other
collateral for all or any of the Secured Obligations or any other assets of such
Pledgor;

         (e) any change, restructuring or termination of the corporate structure
or existence of such Pledgor; or

                                       14
<PAGE>   17
         (f) any other circumstance (including, without limitation, any statute
of limitations) or any existence of or reliance on any representation by the
Collateral Agent, the Trustee, any Holder of the Notes or any other Person,
which might otherwise constitute a defense available to, or a discharge of, any
Pledgor in respect of the Secured Obligations or of this Pledge Agreement.

         SECTION 15. Continuing Security Interest; Termination. This Pledge
Agreement shall create a continuing security interest in and to the Collateral
and shall, unless otherwise provided in this Pledge Agreement or the Indenture,
remain in full force and effect until the payment in full in cash of the Secured
Obligations.

         (b) Upon the consummation of any sale, transfer or other disposition of
Collateral that is permitted by Section 11.02 and 11.03 of the Indenture, the
Collateral Agent shall release the applicable Collateral (but not any proceeds
thereof) to be sold, transferred or disposed of. Any such release shall not
require the consent of any Holder of the Notes. If immediately available cash on
deposit in the Collateral Account is not sufficient to make any distribution to
the Company referred to in the previous sentence, the Collateral Agent shall
liquidate as promptly as practicable Liquid Investments as required to obtain
sufficient cash to make such distribution and, notwithstanding any other
provision of this section, such distribution (other than the distribution of any
immediately available cash then on deposit) shall not be made until such
liquidation has taken place.

         (c) In connection with any release of Collateral, the Company shall
comply with Section 11.02 and Section 11.03 of the Indenture.

         SECTION 17. Additional Pledgors. If a newly acquired or created
Domestic Restricted Subsidiary provides a Note Guaranty pursuant to Section 4.11
of the Indenture or any Subsidiary that is not a party hereto becomes the owner
of any Collateral required to be held in the Cash Collateral Account, such
Person shall immediately become a party hereto by signing and delivering to the
Collateral Agent a Pledge Agreement Supplement, substantially in the form of
Exhibit A, whereupon such Subsidiary shall become a "Pledgor" as defined herein.

         SECTION 18. Successors and Assigns. This Pledge Agreement shall be
binding upon each Pledgor, its transferees, successors and assigns, and shall
inure, together with the rights and remedies of the Collateral Agent hereunder,
to the benefit of the Collateral Agent and the other Secured Parties and their
respective successors, transferees and assigns.

                                       15
<PAGE>   18
         SECTION 19. Miscellaneous Provisions.

         (a) Notices. Any notice or communication given hereunder shall be
sufficiently given if in writing and delivered in person or mailed by first
class mail or facsimile, addressed as follows or to such other address as shall
be designated by any party in a written notice to the other party hereto:

         IF TO THE PLEDGORS:
                  Century Aluminum Company
                  2511 Garden Road
                  Building A Suite 200
                  Monterey, CA 93940
                  Fax: (831) 642-9080
                  Attention: Chief Financial Officer

         IF TO THE COLLATERAL AGENT:
                  Wilmington Trust Company
                  Rodney Square North
                  1100 North Market Street
                  Wilmington, Delaware 19890
                  Attn:  Corporate Trust Department
                  Fax:   (302) 651-8584

All such notices and other communications shall be deemed given if in writing
(i) when delivered in person, (ii) five days after mailing when mailed by first
class mail or (iii) when sent by facsimile transmission, with transmission
confirmed. Any notice to the Collateral Agent will be effective only upon
receipt.

         (b) No Adverse Interpretation of Other Agreements. This Pledge
Agreement may not be used to interpret another pledge, security or debt
agreement of any Pledgor or any subsidiary thereof. No such pledge, security or
debt agreement (other than the Indenture) may be used to interpret this Pledge
Agreement.

         (c) Severability. The provisions of this Pledge Agreement are
severable, and if any clause or provision shall be held invalid, illegal or
unenforceable in whole or in part in any jurisdiction, then such invalidity or
unenforceability shall affect in that jurisdiction only such clause or
provision, or part thereof, and shall not in any manner affect such clause or
provision in any other jurisdiction or any other clause or provision of this
Pledge Agreement in any jurisdiction.

         (d) Table of Contents and Headings. The Table of Contents and headings
of the Sections of this Pledge Agreement have been inserted for

                                       16
<PAGE>   19
convenience of reference only, are not to be considered a part hereof and shall
in no way modify or restrict any of the terms or provisions hereof.

         (e) Counterparts. This Pledge Agreement may be signed in two or more
counterparts, each of which shall be deemed an original, but all of which shall
together constitute one and the same agreement.

         (f) Benefits of Pledge Agreement. Nothing in this Pledge Agreement,
express or implied, shall give to any person, other than the parties hereto and
their successors hereunder, and the Trustee and the Holders of the Notes, any
benefit or any legal or equitable right, remedy or claim under this Pledge
Agreement.

         (g) Amendments, Waiver and Consents. Any amendment or waiver of any
provision of this Pledge Agreement and any consent to any departure by any
Pledgor from any provision of this Pledge Agreement shall be effective only if
in writing, signed by the Collateral Agent and made or duly given in compliance
with all of the terms and provisions of the Indenture, and then such waiver or
consent shall be effective only in the specific instance and for the specific
purpose for which given. None of the Collateral Agent or any other Secured Party
shall be deemed, by any act, delay, indulgence, omission or otherwise, to have
waived any right or remedy hereunder or to have acquiesced in any Default or
Event of Default or in any breach of any of the terms and conditions hereof.
Failure of the Collateral Agent or any other Secured Party to exercise, in whole
or in part, or delay in exercising, any right, power or privilege hereunder
shall not preclude any other or further exercise thereof or the exercise of any
other right, power or privilege. A waiver by the Collateral Agent or any other
Secured Party of any right or remedy hereunder on any one occasion shall not be
construed as a bar to any right or remedy that the Collateral Agent or any other
Secured Party would otherwise have on any future occasion. The rights and
remedies herein provided are cumulative, may be exercised singly or concurrently
and are not exclusive of any rights or remedies provided by law.

         (h) Interpretation of Agreement. To the extent a term or provision of
this Pledge Agreement conflicts with the Indenture, the Indenture shall control
with respect to the subject matter of such term or provision. Acceptance of or
acquiescence in a course of performance rendered under this Pledge Agreement
shall not be relevant to determine the meaning of this Pledge Agreement even
though the accepting or acquiescing party had knowledge of the nature of the
performance and opportunity for objection.

         (i) Authority of the Collateral Agent. The Collateral Agent shall have
and be entitled to exercise all powers hereunder that are specifically granted
to the Collateral Agent by the terms hereof, together with such powers as are

                                       17
<PAGE>   20
reasonably incident thereto. The Collateral Agent may perform any of its duties
hereunder or in connection with the Collateral by or through agents or employees
and shall be entitled to retain counsel and to act in reliance upon the advice
of counsel concerning all such matters. Except as otherwise expressly provided
in this Pledge Agreement or the Indenture, neither the Collateral Agent nor any
director, officer, employee, attorney or agent of the Collateral Agent shall be
liable to any Pledgor for any action taken or omitted to be taken by the
Collateral Agent, in its capacity as Collateral Agent, hereunder, except for its
own negligence or willful misconduct, and the Collateral Agent shall not be
responsible for the validity, effectiveness or sufficiency hereof or of any
document or security furnished pursuant hereto. The Collateral Agent and its
directors, officers, employees, attorneys and agents shall be entitled to rely
on any communication, instrument or document believed by it or them to be
genuine and correct and to have been signed or sent by the proper Person or
Persons.

                  (ii) Each Pledgor acknowledges that the rights and
         responsibilities of the Collateral Agent under this Pledge Agreement
         with respect to any action taken by the Collateral Agent or the
         exercise or non-exercise by the Collateral Agent of any option, right,
         request, judgment or other right or remedy provided for herein or
         resulting or arising out of this Pledge Agreement shall, as between the
         Collateral Agent and the other Secured Parties, be governed by the
         Indenture and by such other agreements with respect thereto as may
         exist from time to time among them, but, as between the Collateral
         Agent and the Pledgors, the Collateral Agent shall be conclusively
         presumed to be acting as agent for the Secured Parties with full and
         valid authority so to act or refrain from acting, and the Pledgors
         shall not be obligated or entitled to make any inquiry respecting such
         authority.

         (j) Appointment of Co-Agents. At any time or times, in order to comply
with any legal requirement in any jurisdiction, the Collateral Agent may appoint
another bank or trust company or one or more other persons (provided that,
unless such approval would impair the perfection of the Lien purported to be
granted hereunder, the bank or trust company or person or persons appointed
shall be approved by the Company, which approval shall not unreasonably
withheld), either to act as co-agent or co-agents, jointly with the Collateral
Agent, or to act as separate agent or agents on behalf of the Secured Parties
with such power and authority as may be necessary for the effectual operation of
the provisions hereof and may be specified in the instrument of appointment
(which may, in the discretion of the Collateral Agent, include provisions for
the protection of such co-agent or separate agent similar to the provisions of
Section 12 and Section 14). Any such co-agent or separate agent shall agree in
writing to comply with all of

                                       18
<PAGE>   21
the obligations of the Collateral Agent hereunder applicable to the power and
authority it is granted by the Collateral Agent pursuant to this clause (j).

         (k) Rights of Holders of the Notes. No Holder of Notes shall have any
independent rights hereunder other than those rights granted to individual
Holders of the Notes pursuant to Section 6.06 of the Indenture; provided that
nothing in this subsection shall limit any rights granted to the Trustee under
the Notes or the Indenture.

         (l) Governing Law; Submission to Jurisdiction; Waiver of Damages and
Bonds.

                  (i) This Pledge Agreement shall be governed by and construed
         in accordance with the laws of the State of New York, except as
         otherwise required by mandatory provisions of law (whether under the
         UCC as in effect in the State of New York or the Federal Book Entry
         Regulations) and except to the extent that remedies provided by the
         laws of any jurisdiction other than the State of New York are governed
         by the laws of such jurisdiction.

                  (ii) Each Pledgor hereby agrees to submit to the jurisdiction
         of any state or Federal court located in the Borough of Manhattan, City
         of New York.

                  (iii) Each Pledgor agrees that it will not assert any
         counterclaims, setoffs or crossclaims in any proceeding brought by the
         Collateral Agent to realize on such property or to enforce a judgment
         or other court order in favor of the Collateral Agent, except for such
         counterclaims, setoffs or crossclaims which, if not asserted in any
         such proceeding, could not otherwise be brought or asserted.

                  (iv) Each Pledgor waives any objection that it may have to the
         location of a court in The City of New York once the Collateral Agent
         has commenced a proceeding described in this Section 19(l) including,
         without limitation, any objection to the laying of venue or based on
         the grounds of forum non conveniens.

                  (v) Each Pledgor agrees that no Holder of Notes or (except as
         otherwise provided in this Pledge Agreement or the Indenture) the
         Collateral Agent or the Trustee in their respective capacities as such
         shall have any liability to such Pledgor (whether arising in tort,
         contract or otherwise) for losses suffered by such Pledgor in
         connection with, arising out of, or in any way related to, the
         transactions contemplated and the relationship established by this
         Pledge Agreement, or any act, omission or event occurring in connection
         therewith, except that the Collateral Agent shall be liable if it is

                                       19
<PAGE>   22
         determined by a final and nonappealable judgment of a court that is
         binding on the Collateral Agent that such losses were the result of
         acts or omissions on the part of the Collateral Agent constituting bad
         faith, gross negligence (unless otherwise required by the Trust
         Indenture Act) or willful misconduct.

                  (vi) To the extent permitted by applicable law, each Pledgor
         waives the posting of any bond otherwise required of the Collateral
         Agent or any other Secured Party in connection with any judicial
         process or proceeding to enforce any judgment or other court order
         pertaining to this Pledge Agreement or any related agreement or
         document entered in favor of any Secured Party or to enforce by
         specific performance, temporary restraining order or preliminary or
         permanent injunction this Pledge Agreement or any related agreement or
         document between the Pledgors on the one hand and the Secured Parties
         on the other hand.

                                       20
<PAGE>   23
         IN WITNESS WHEREOF, each Pledgor and the Collateral Agent have each
caused this Pledge Agreement to be duly executed and delivered as of the date
first above written. (i)

                            PLEDGORS:
                            CENTURY ALUMINUM COMPANY

                            By:
                               --------------------------------------
                                      Name:
                                     Title:

                            CENTURY ALUMINUM OF
                            WEST VIRGINIA, INC.

                            By:
                              ---------------------------------------
                                      Name:
                                     Title:

                            BERKELEY ALUMINUM,  INC.

                            By:
                              ---------------------------------------
                                      Name:
                                     Title:

                            CENTURY KENTUCKY, INC.

                            By:
                              --------------------------------------
                                      Name:
                                     Title:

                            VIRGIN ISLANDS ALUMINA
                            CORPORATION, LLC.

                            By:
                              -------------------------------------
                                      Name:

                                       21
<PAGE>   24
                                    Title:
                            METALSCO LTD.

                            By:
                              --------------------------------------
                                      Name:
                                     Title:

                            SKYLINER, INC.

                            By:
                              --------------------------------------
                                      Name:
                                     Title:

                            NSA, LTD.

                            By:
                              ---------------------------------------
                                      Name:
                                     Title:

                            COLLATERAL AGENT:
                            WILMINGTON TRUST COMPANY

                            By:
                              ---------------------------------------
                                      Name:
                                     Title:
<PAGE>   25
                                                                       EXHIBIT A

                           PLEDGE AGREEMENT SUPPLEMENT

         PLEDGE AGREEMENT SUPPLEMENT dated as of _______, ____, between [Name of
New Pledgor] (the "NEW PLEDGOR") and Wilmington Trust Company, as Collateral
Agent.

         WHEREAS, Century Aluminum Company, the other Pledgors party thereto and
Wilmington Trust Company, as Collateral Agent, are parties to a Pledge and
Security Agreement dated as of April 2, 2001 (as heretofore amended and/or
supplemented, the "PLEDGE AGREEMENT") under which Century Aluminum Company and
the other Pledgors secures certain obligations;

         WHEREAS, [name of New Pledgor] is required to become a party to the
Security Agreement as a Pledgor thereunder; and

         WHEREAS, terms defined in the Pledge Agreement (or whose definitions
are incorporated by reference in Section 1 of the Pledge Agreement) and not
otherwise defined herein have, as used herein, the respective meanings provided
for therein;

         NOW, THEREFORE, in consideration of the foregoing and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto agree as follows:

         SECTION 1. Party to the Pledge Agreement. The New Pledgor acknowledges
that, by signing this Pledge Agreement Supplement and delivering it to the
Collateral Agent, the New Pledgor becomes a "Pledgor" for all purposes of the
Pledge Agreement and will thereafter have all the rights and obligations of a
Pledgor thereunder and be bound by all the provisions thereof as fully as if the
New Pledgor were one of the original parties thereto.

         SECTION 2. Pledge and Grant of Security Interest. In order to secure
the Secured Obligations, the New Pledgor grants to the Collateral Agent for the
benefit of the Secured Parties a continuing security interest in and to all of
such Pledgor's right, title and interest in and to all of the following, whether
now owned or hereafter acquired by such Pledgor, wherever located and whether
now or hereafter existing or arising (hereinafter collectively referred to as
the "NEW COLLATERAL"), whether characterized as investment property, general
intangibles or otherwise:

                                       2
<PAGE>   26
         (a) the Cash Collateral Account;

         (b)all cash, monies, investment property, instruments and financial
assets (including without limitation, the Liquid Investments) held in the Cash
Collateral Account;

         (c) all Cash Proceeds, whether or not held in the Cash Collateral
Account;

         (d) all dividends, interest, cash, monies and other property from time
to time received, receivable or otherwise distributed or distributable in
respect of, or in exchange for, any or all such Collateral; and

         (e) all proceeds of any of the foregoing clauses (a) through (d).

         SECTION 3. Delivery of Collateral. Concurrently with delivering this
Pledge Agreement Supplement to the Administrative Agent, the New Pledgor is
complying with the provisions of Section 5 of the Security Agreement with
respect to any New Collateral owned by it on the date hereof.

         SECTION 4. Representations and Warranties. Each of the representations
and warranties set forth in Section 7 of the Pledge Agreement is true as applied
to the New Pledgor and the New Collateral on the date hereof. For purposes of
the foregoing sentence, references in said Sections to a "Pledgor" shall be
deemed to refer to the New Pledgor and references to "Collateral" shall be
deemed to refer to the New Collateral.

         SECTION 5. Governing Law. This Pledge Agreement Supplement shall be
construed in accordance with and governed by the laws of the State of New York.

                                       3
<PAGE>   27

         IN WITNESS WHEREOF, the parties hereto have caused this Pledge
Agreement Supplement to be duly executed by their respective authorized officers
as of the day and year first above written.

                                       [NAME OF NEW PLEDGOR]

                                       By:
                                         ---------------------------------------
                                          Name:
                                          Title:

                                       WILMINGTON TRUST COMPANY, as
                                       Collateral Agent

                                       By:
                                         ---------------------------------------
                                          Name:
                                          Title:

                                       4<PAGE>   1
                                                                     Exhibit 4.7

                 CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT

                                 BY AND BETWEEN

                            CENTURY ALUMINUM COMPANY

                                       AND

                                   GLENCORE AG

Dated as of March 30, 2001
<PAGE>   2
                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                                     PAGE
<S>                                                                                                  <C>
ARTICLE I CERTAIN DEFINITIONS..........................................................................1

    Section 1.1 Certain Definitions....................................................................1

ARTICLE II PURCHASE OF SHARES..........................................................................2

    Section 2.1 Purchase of Shares; Closing............................................................2

ARTICLE III REPRESENTATIONS AND WARRANTIES.............................................................3

    Section 3.1 Representations and Warranties of the Company..........................................3
    Section 3.2 Representations and Warranties of the Purchaser........................................6

ARTICLE IV OTHER AGREEMENTS OF THE PARTIES.............................................................8

    Section 4.1 Transfer Restrictions..................................................................8
    Section 4.2 Furnishing of Information..............................................................9
    Section 4.3 Notice of Certain Events...............................................................9
    Section 4.4 Blue Sky Laws..........................................................................9
    Section 4.5 Integration............................................................................9
    Section 4.6 Filing of Reports......................................................................9
    Section 4.7 Furnishing of Rule 144A Materials......................................................9
    Section 4.8 Solicitation Materials................................................................10
    Section 4.9 Matters Affecting Purchaser's Rights..................................................10
    Section 4.10 HSR Act Filings......................................................................10

ARTICLE V CONDITIONS PRECEDENT TO CLOSING.............................................................10

    Section 5.1 Conditions Precedent to Obligations of the Purchaser..................................10
    Section 5.2 Conditions Precedent to Obligations of the Company....................................11

ARTICLE VI TERMINATION................................................................................12

    Section 6.1 Termination by Mutual Consent.........................................................12
    Section 6.2 Termination by the Company or the Purchaser...........................................12

ARTICLE VII MISCELLANEOUS.............................................................................12

    Section 7.1 Fees and Expenses.....................................................................12
    Section 7.2 Entire Agreement......................................................................13
    Section 7.3 Notices...............................................................................13
    Section 7.4 Indemnification.......................................................................14
    Section 7.5 Arbitration...........................................................................14
    Section 7.6 Amendments; Waivers...................................................................14
    Section 7.7 Headings..............................................................................14
    Section 7.8 Successors and Assigns................................................................14
    Section 7.9 No Third Party Beneficiaries..........................................................14
    Section 7.10 Governing Law........................................................................14
    Section 7.11 Survival.............................................................................15
    Section 7.12 Counterpart Signatures...............................................................15
</TABLE>

                                       i
<PAGE>   3
<TABLE>
<CAPTION>
<S>                                                                                                   <C>
    Section 7.13 Publicity............................................................................15
    Section 7.14 Severability.........................................................................15
    Section 7.15 Remedies.............................................................................15
</TABLE>

Exhibit A  Certificate of Designation
Exhibit B  Form of Opinion of internal counsel to Century Aluminum Company
Exhibit C  Certificate of Officers of Century Aluminum Company

                                      -ii-
<PAGE>   4
           CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT, dated as of March 30,
2001 (this "Agreement"), by and between Century Aluminum Company, a Delaware
corporation (the "Company"), and Glencore AG, a Swiss company (the "Purchaser").

           WHEREAS, the Company desires to issue and sell to the Purchaser and
the Purchaser desires to acquire shares of the Company's 8% Cumulative
Convertible Preferred Stock, $0.01 par value per share (the "Preferred Stock").

           NOW, THEREFORE, in consideration of the mutual covenants and
agreements set forth herein and for good and valuable consideration, the receipt
and sufficiency of which is hereby acknowledged, the parties agree as follows:

                                   ARTICLE I

                               CERTAIN DEFINITIONS

           Section 1.1 Certain Definitions. As used in this Agreement, and
unless the context requires a different meaning, the following terms have the
meanings indicated:

           "Affiliate" means, with respect to any Person, any Person that,
directly or indirectly, controls, is controlled by or is under common control
with such Person. For the purposes of this definition, "control" (including,
with correlative meanings, the terms "controlled by" and "under common control
with") shall mean the possession, directly or indirectly, of the power to direct
or cause the direction of the management and policies of such Person, whether
through the ownership of voting securities, by contract or otherwise.

           "Business Day" shall mean a day (other than a Saturday or Sunday) on
which commercial banks are open for business in London, Switzerland and New
York.

           "Certificate of Designation" shall have the meaning set forth in
Section 2.1(a).

           "Closing" shall have the meaning set forth in Section 2.1(b).

           "Closing Date" shall have the meaning set forth in Section 2.1(b).

           "Common Stock" shall mean the Company's common stock, par value $0.01
per share.

           "Exchange Act" shall mean the Securities Exchange Act of 1934, as
amended.

           "Financial Statements" shall have the meaning set forth in Section
3.1(j).

           "HSR Act" shall mean the Hart-Scott-Rodino Antitrust Improvements Act
of 1976, as amended.

           "Lien" shall mean, with respect to any asset, any mortgage, lien,
pledge, encumbrance, charge or security interest of any kind in or on such asset
or the revenues or income thereon or therefrom.

                                       1
<PAGE>   5
           "Material Adverse Effect" shall have the meaning set forth in Section
3.1(a).

           "NASD" shall mean the National Association of Securities Dealers,
Inc.

           "Offering Circular" shall mean the Preliminary Offering Circular
dated March 9, 2001 relating to the Senior Secured Mortgage Notes of the Company
due 2008.

           "Per Share Consideration" shall have the meaning set forth in Section
2.1(a).

           "Person" shall mean an individual or a corporation, partnership,
trust, incorporated or unincorporated association, joint venture, limited
liability company, joint stock company, government (or an agency or political
subdivision thereof) or other entity of any kind.

           "Preferred Stock" shall have the meaning set forth in the recitals
hereto.

           "Purchase Price" shall have the meaning set forth in Section 2.1(a).

           "SEC" shall mean the U.S. Securities and Exchange Commission.

           "SEC Documents" shall have the meaning set forth in Section 3.1(j).

           "Securities Act" shall mean the Securities Act of 1933, as amended.

           "Shares" shall have the meaning set forth in Section 2.1(a).

           "Subsidiaries" shall have the meaning set forth in Section 3.1(a).

           "Underlying Shares" shall mean the shares of Common Stock into which
the Shares are convertible in accordance with the terms hereof and the
Certificate of Designation.

                                   ARTICLE II

                               PURCHASE OF SHARES

           Section 2.1 Purchase of Shares; Closing. (a) Subject to the terms and
conditions herein set forth, the Company shall issue and sell to the Purchaser,
and the Purchaser shall purchase from the Company on the Closing Date 500,000
shares of the Preferred Stock (the "Shares"), which shall have the respective
rights, preferences and privileges set forth in Exhibit A hereto (the
"Certificate of Designation") for an aggregate purchase price of US$25,000,000
(the "Purchase Price"); and a per share price of US$50 (the "Per Share
Consideration").

               (b) The closing of the purchase and sale of the Shares (the
"Closing") shall take place at the offices of Curtis, Mallet-Prevost, Colt &
Mosle LLP immediately following the execution hereof, or at such other time
and/or place as the Purchaser and the Company may agree, provided, however, in
no case shall the Closing take place later than April 30, 2001. The date of the
Closing is hereinafter referred to as the "Closing Date".

               (c) At the Closing, (i) the Company shall deliver to the
Purchaser (A) one or more stock certificates representing the Shares purchased
hereunder, registered in the name of

                                      -2-
<PAGE>   6
the Purchaser and (B) all other documents, instruments and writings required to
have been delivered at or prior to Closing by the Company pursuant to this
Agreement and (ii) the Purchaser shall deliver to the Company (A) the Purchase
Price in United States dollars in immediately available funds by wire transfer
to an account designated in writing by the Company at least two Business Days
prior to the Closing and (B) all other documents, instruments and writings
required to have been delivered at or prior to Closing by the Purchaser pursuant
to this Agreement.

                             ARTICLE III

                         REPRESENTATIONS AND WARRANTIES

           Section 3.1 Representations and Warranties of the Company. The
Company hereby represents and warrants to the Purchaser as follows:

(a) Organization and Qualification. The Company and each of its subsidiaries on
the date hereof (the "Subsidiaries") is a corporation, duly incorporated,
validly existing and in good standing under the laws of the jurisdiction of its
incorporation, with the requisite corporate power and authority to own and use
its properties and assets and to carry on its business as currently conducted.
Each of the Company and the Subsidiaries is duly qualified to do business and is
in good standing as a foreign corporation in each jurisdiction in which the
nature of the business conducted or property owned by it makes such
qualification necessary, except where the failure to be so qualified or in good
standing, as the case may be, has not had and could not reasonably be expected
to have, individually or in the aggregate, a material adverse effect on the
condition (financial or otherwise), business, operations, assets or prospects of
the Company and the Subsidiaries, taken as a whole, or on the ability of the
Company to consummate the transactions contemplated hereby (a "Material Adverse
Effect").

               (b) Authorization; Enforcement. The Company has the requisite
corporate power and authority to enter into and to consummate the transactions
contemplated hereby and otherwise to carry out its obligations hereunder. The
execution and delivery of this Agreement by the Company and the consummation by
it of the transactions contemplated hereby have been duly authorized by all
necessary action on the part of the Company. This Agreement has been duly
executed and delivered by the Company and constitutes the legal, valid and
binding obligation of the Company enforceable against the Company in accordance
with its terms, except as such enforceability may be limited by applicable
bankruptcy, insolvency, reorganization, moratorium, liquidation or similar laws
relating to, or affecting generally the enforcement of, creditors' rights and
remedies or by other equitable principles of general application.

               (c) Capitalization. Subject to the vesting of additional
performance share units, the authorized, issued and outstanding capital stock of
the Company is as set forth in the SEC Documents. All outstanding shares of
capital stock of the Company are duly authorized, validly issued, fully paid and
non-assessable. No shares of capital stock of the Company are entitled to
preemptive or similar rights. Other than additional option grants in an
aggregate of not more than 25,000 options and except as disclosed in the SEC
Documents, other than the Shares, there are no outstanding options, warrants,
script rights to subscribe to, calls or commitments of any character whatsoever
relating to, or securities, rights or obligations convertible into or

                                      -3-
<PAGE>   7
exchangeable for, or giving any Person any right to subscribe for or acquire any
shares of capital stock, or contracts, commitments, understandings, or
arrangements by which the Company or any Subsidiary is or may become bound to
issue additional shares of capital stock, or securities or rights convertible or
exchangeable into shares of capital stock of the Company. Neither the Company
nor any Subsidiary is in violation of any of the provisions of its respective
certificate of incorporation, bylaws or other constituent documents. Other than
as set forth in the SEC Documents or the Offering Circular, there are no
outstanding rights (other than those of which have been satisfied) which permit
the holder thereof to cause the Company to file a registration statement under
the Securities Act or which permit the holder thereof to include securities of
the Company in a registration statement filed by the Company under the
Securities Act, and there are no outstanding agreements or other commitments
which otherwise relate to the registration of any securities of the Company
under the Securities Act. All securities of the Company heretofore issued and
sold by the Company were issued and sold in compliance with all applicable
Federal and state securities laws. Assuming that the representations and
warranties of the Purchaser set forth in Section 3.2 are true and correct, the
offering, issuance and sale of the Shares and the Underlying Shares will be
exempt from the registration requirements of the Securities Act and applicable
state securities laws.

               (d) Issuance of Shares. The Shares are duly authorized and, when
issued and paid for in accordance with the terms hereof, shall be validly
issued, fully paid and nonassessable. The Company has and at all times while the
Shares are outstanding will maintain an adequate reserve of shares of Common
Stock to enable it to perform its obligations under this Agreement and the
Certificate of Designation. When issued in accordance with the terms hereof and
the Certificate of Designation, the Underlying Shares will be duly authorized,
validly issued, fully paid and nonassessable. The issuance of the Shares and the
Underlying Shares will not be subject to any pre-emptive rights or similar
rights with respect to such Shares or such Underlying Shares.

               (e) No Conflicts. The execution, delivery and performance of this
Agreement by the Company and the consummation by the Company of the transactions
contemplated hereby do not and will not (i) conflict with or violate any
provision of its certificate of incorporation or bylaws, or (ii) conflict with,
or constitute a default (or an event which with notice or lapse of time or both
would become a default) under, or give to others any rights of termination,
amendment, acceleration or cancellation of, any agreement, indenture or
instrument to which the Company or any Subsidiary is a party), or by which any
property or asset of the Company or any Subsidiary is bound or affected, or
(iii) result in a violation of any law, rule, regulation, order, judgment,
injunction, decree or other restriction of any court or governmental authority
to which the Company or its Subsidiaries is subject (including Federal and state
securities laws and regulations), or by which any property or asset of the
Company or any Subsidiary is bound or affected.

               (f) Consents and Approvals. Except for the filing of the
Certificate of Designation and any required approvals under the HSR Act, neither
the Company nor any Subsidiary is required to obtain any consent, waiver,
authorization or order of, or make any filing or registration with, any court or
other federal, state, local or other governmental authority having jurisdiction
over the Company or other Person in connection with (i) the execution, delivery
and performance by the Company of this Agreement, (ii) the valid and lawful

                                      -4-
<PAGE>   8
authorization, issuance, sale and delivery of the Shares or (iii) the valid and
lawful authorization, reservation, issuance, sale and delivery of the Underlying
Shares.

               (g) Litigation; Proceedings. Except as disclosed in the SEC
Documents, there is no action, suit, notice of violation, proceeding or
investigation pending or, to the best knowledge of the Company, threatened
against the Company or any of its Subsidiaries or any of their respective
properties before or by any court, arbitral tribunal or panel, or governmental
or administrative agency or regulatory authority (Federal, State, county, local
or foreign) which (i) relates to or challenges the legality, validity or
enforceability of this Agreement, the Shares or the Underlying Shares, (ii)
could reasonably be expected to, individually or in the aggregate, have a
Material Adverse Effect or (iii) could reasonably be expected to, individually
or in the aggregate, materially impair the ability of the Company to perform
fully and on a timely basis its obligations under this Agreement.

               (h) No Default or Violation. Neither the Company nor any
Subsidiary (i) is in default under or in violation of any indenture, loan or
credit agreement or any other agreement or instrument to which it is a party or
by which it or any of its properties is bound, except such conflicts or defaults
as could not reasonably be expected to have a Material Adverse Effect, (ii) is
in violation of any order of any court, arbitral tribunal, panel or governmental
body, except for such violations as could not reasonably be expected to have a
Material Adverse Effect, or (iii) is in violation of any statute, rule or
regulation of any governmental authority which could (individually or in the
aggregate) (x) adversely affect the legality, validity or enforceability of this
Agreement, (y) reasonably be expected to have a Material Adverse Effect or (z)
adversely impair the Company's ability or obligation to perform fully on a
timely basis its obligations under this Agreement.

               (i) Private Offering. Neither the Company nor any Person acting
on its behalf has taken or will take any action (including, without limitation,
any offering of any securities of the Company under circumstances which would
require the integration of such offering with the offering of the Shares under
the Securities Act) which might subject the offering, issuance or sale of the
Shares to the registration requirements of Section 5 of the Securities Act.

               (j) SEC Documents. The Company has filed with the SEC all reports
and registration statements and other filings required to be filed by it under
the rules and regulations of the SEC, for the two years preceding the date
hereof (the foregoing materials being collectively referred to herein as the
"SEC Documents") on a timely basis. As of their respective dates, the SEC
Documents complied in all material respects with the requirements of the
Securities Act and the Exchange Act and the rules and regulations of the SEC
promulgated thereunder, and none of the SEC Documents, when filed, contained any
untrue statement of a material fact or omitted to state a material fact required
to be stated therein or necessary in order to make the statements therein, in
light of the circumstances under which they were made, not misleading. The
financial statements of the Company, including the notes thereto, included in
the SEC Documents (the "Financial Statements") were complete and correct in all
material respects as of their respective dates, complied as to form in all
material respects with applicable accounting requirements and with the published
rules and regulations of the SEC with respect thereto as of their respective
dates, and were prepared in accordance with generally accepted

                                      -5-
<PAGE>   9
accounting principles applied on a basis consistent throughout the periods
indicated (except as may be indicated in the notes thereto or, in the case of
unaudited statements included in Quarterly Reports on Form 10-Q, as permitted by
Form 10-Q of the SEC). The Financial Statements fairly present the financial
condition and operating results of the Company and its Subsidiaries at the dates
and for the periods indicated therein (subject, in the case of unaudited
statements, to normal year-end adjustments). There has been no change in the
Company's accounting policies except as described in the notes to the Financial
Statements.

               (k) Absence of Certain Charges.

           Except as otherwise disclosed in the SEC Documents or the Offering
Circular, since December 31, 2000, there has not been:

               (i) Any material change in the assets, liabilities, financial
condition, business or results of operations of the Company and its Subsidiaries
from that reflected in the Financial Statements, except changes in the ordinary
course of business which could not reasonably be expected to, either
individually or in the aggregate, constitute a Material Adverse Effect;

               (ii) Any change in the contingent obligations of the Company or
its Subsidiaries, whether by way of guaranty, endorsement, indemnity, warranty
or otherwise, except such changes as could not reasonably be expected to, either
individually or in the aggregate, constitute a Material Adverse Effect;

               (iii) Any damage, destruction or loss, whether or not covered by
insurance, which could reasonably be expected to have a Material Adverse Effect;

               (iv) With the exception of payments of cash dividends, any
declaration, setting aside or payment of any dividend or other distribution of
the assets or securities of the Company in respect of outstanding capital stock
of the Company;

               (v) Any material contract entered into by the Company or any of
its Subsidiaries, other than in the ordinary course of business and as provided
to the Purchaser, or any material amendment or termination of, or default under,
any material contract to which the Company or any of its Subsidiaries is a party
or by which any of them are bound;

               (vi) Any commitment or agreement by the Company or any of its
Subsidiaries to do any of the things described in the preceding clauses (i)
through (v); or

               (vii) Any other event or condition of any character that has had
or that could reasonably be expected to have a Material Adverse Effect.

           Section 3.2 Representations and Warranties of the Purchaser. The
Purchaser hereby represents and warrants to the Company as follows:

               (a) Organization; Authority. The Purchaser is a corporation duly
and validly existing and in good standing under the laws of Switzerland. The
Purchaser has the requisite power and authority to enter into and to consummate
the transactions contemplated hereby and

                                      -6-
<PAGE>   10
otherwise to carry out its obligations hereunder. The purchase of the Shares by
the Purchaser hereunder has been duly authorized by all necessary action on the
part of the Purchaser. This Agreement has been duly executed and delivered by
the Purchaser and constitutes the valid and legally binding obligation of the
Purchaser, enforceable against the Purchaser in accordance with its terms,
subject to bankruptcy, insolvency, fraudulent transfer, reorganization,
moratorium and similar laws of general applicability relating to or affecting
creditors' rights generally and to general principles of equity.

               (b) Consents and Approvals. The Purchaser is not required to
obtain any consent, waiver, authorization or order of, or make any filing or
registration with, any court or other federal, state, local or other
governmental authority having jurisdiction over the Purchaser or other Person in
connection with the execution, delivery and performance by the Purchaser of this
Agreement.

               (c) Litigation; Proceedings. There is no action, suit, notice of
violation, proceeding or investigation pending or, to the best knowledge of the
Purchaser, threatened against the Purchaser before or by any court, arbitral
tribunal or panel, or governmental or administrative agency or regulatory
authority (Federal, State, county, local or foreign) which (i) relates to or
challenges the legality, validity or enforceability of this Agreement or (ii)
could reasonably be expected to, individually or in the aggregate, materially
impair the ability of the Purchaser to perform fully and on a timely basis its
obligations under this Agreement.

               (d) Investment Intent. The Purchaser is acquiring the Shares and
the Underlying Shares for its own account for investment purposes only and not
with a view to or for distributing or reselling such Shares or Underlying Shares
or any part thereof or interest therein in violation of the Securities Act,
without prejudice, however, to the Purchaser's right, subject to the provisions
of this Agreement, at all times to sell or otherwise dispose of all or any part
of such Shares or Underlying Shares under an effective registration statement
under the Securities Act and in compliance with applicable State securities laws
or in a transaction exempt from, or outside the scope of such registration
requirements.

               (e) Purchaser Status. At the time the Purchaser was offered the
Shares, it was, and at the date hereof, it is, and at the Closing Date, it will
be, an "accredited investor" as defined in Rule 501(a) under the Securities Act.

               (f) Experience of Purchaser. The Purchaser, either alone or
together with its representatives, has such knowledge, sophistication and
experience in business and financial matters so as to be capable of evaluating
the merits and risks of the prospective investment in the Shares, and has so
evaluated the merits and risks of such investment.

               (g) Ability of Purchaser to Bear Risk of Investment. The
Purchaser is able to bear the economic risk of an investment in the Shares and,
at the present time, is, and at the Closing Date it will be, able to afford a
complete loss of such investment.

               (h) Access to Information. The Purchaser acknowledges that it has
been afforded (i) the opportunity to ask such questions as it has deemed
necessary of, and to receive answers from, representatives of the Company
concerning the terms and conditions of the

                                      -7-
<PAGE>   11
offering of the Shares and the merits and risks of investing in the Shares, (ii)
access to information about the Company and the Company's financial condition,
results of operations, business, properties, management and prospects sufficient
to enable it to evaluate its investment in the Common Stock, and (iii) the
opportunity to obtain such additional information which the Company possesses or
can acquire without unreasonable effort or expense that is necessary to make an
informed investment decision with respect to the Shares.

                                   ARTICLE IV

                         OTHER AGREEMENTS OF THE PARTIES

           Section 4.1 Transfer Restrictions. If the Purchaser should decide to
dispose of any of the Shares to be purchased by it hereunder (and upon
conversion thereof, any Underlying Shares), the Purchaser understands and agrees
that it may do so only (i) pursuant to an effective registration statement under
the Securities Act, (ii) to the Company or (iii) pursuant to an available
exemption from or in a transaction not subject to registration under the
Securities Act. In connection with any transfer of any Shares other than
pursuant to an effective registration statement or to the Company, the Company
may require that the transferor of such Shares provide to the Company, at the
transferor's expense, an opinion of counsel experienced in the area of United
States securities laws selected by the transferor and reasonably acceptable to
the Company, the form and substance of which opinion shall be reasonably
satisfactory to the Company, to the effect that such transfer does not require
registration of such Shares under the Securities Act or any State securities
laws.

           The Purchaser agrees to the imprinting of the following legend on
certificates representing the Shares:

           NEITHER THESE SECURITIES NOR THE SECURITIES INTO WHICH THESE
SECURITIES ARE CONVERTIBLE HAVE BEEN REGISTERED WITH THE SECURITIES AND EXCHANGE
COMMISSION OR THE SECURITIES COMMISSION OF ANY STATE IN RELIANCE UPON AN
EXEMPTION FROM REGISTRATION UNDER THE U.S. SECURITIES ACT OF 1933, AS AMENDED
(THE "SECURITIES ACT"), AND, ACCORDINGLY, THEY MAY NOT BE OFFERED OR SOLD WITHIN
THE UNITED STATES OR TO, OR FOR THE ACCOUNT OR BENEFIT OF, U.S. PERSONS EXCEPT
(A) PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT UNDER THE SECURITIES ACT, OR
(B) PURSUANT TO AN AVAILABLE EXEMPTION FROM REGISTRATION UNDER THE SECURITIES
ACT.

           The legend set forth above may be removed if and when the Shares
represented by such certificate or the Underlying Shares, as the case may be,
are disposed of pursuant to an effective registration statement under the
Securities Act or in the opinion of counsel to the Company experienced in the
area of United States securities laws such legend is no longer required under
applicable requirements of the Securities Act or any state securities laws. The
stock certificates representing the Shares and the Underlying Shares shall also
bear any other legends required by applicable Federal or state securities laws,
which legends may be removed when, in the opinion of counsel to the Company
experienced in the area of the applicable securities laws, such legends are no
longer required under the applicable requirements of such securities laws. The
Company

                                      -8-
<PAGE>   12
agrees that it will provide the Purchaser, upon request, with a substitute stock
certificate or certificates, free from such legend at such time as such legend
is determined to be no longer applicable. The Company makes no representation,
warranty or agreement as to the availability, now or hereafter, of any exemption
from registration under the Securities Act with respect to any resale of Shares
or Underlying Shares.

           Section 4.2 Furnishing of Information. As long as the Purchaser owns
any Shares, if requested, the Company will promptly furnish to it all reports
filed by the Company pursuant to Section 13(a) or 15(d) of the Exchange Act (or
if the Company is not at the time required to file reports pursuant to such
sections, unaudited quarterly and audited annual financial statements prepared
in accordance with generally accepted accounting principles).

           Section 4.3 Notice of Certain Events. The Company shall (i) advise
the Purchaser promptly after obtaining knowledge thereof, and, if requested by
the Purchaser, confirm such advice in writing, of the issuance by any state
securities commission of any stop order suspending the qualification or
exemption from qualification of the Shares or the Common Stock for offering or
sale in any jurisdiction, or the initiation of any proceeding for such purpose
by any state securities commission or other regulatory authority, (ii) use its
best efforts to prevent the issuance of any stop order or order suspending the
qualification or exemption from qualification of the Shares or the Common Stock
under any state securities or Blue Sky laws, and (iii) if at any time any state
securities commission or other regulatory authority shall issue an order
suspending the qualification or exemption from qualification of the Shares or
the Common Stock under any such laws, use its best efforts to obtain the
withdrawal or lifting of such order at the earliest possible time.

           Section 4.4 Blue Sky Laws. The Company shall cooperate with the
Purchaser in connection with the qualification of the Shares and the Underlying
Shares under the securities or Blue Sky laws of such jurisdictions as the
Purchaser may request and to continue such qualification at all times; provided,
however, that neither the Company nor its Subsidiaries shall be required in
connection therewith to qualify as a foreign corporation where they are not now
so qualified.

           Section 4.5 Integration. The Company shall not and shall use its best
efforts to ensure that no Affiliate shall sell, offer for sale or solicit offers
to buy or otherwise negotiate in respect of any security (as defined in Section
2 of the Securities Act) that would be integrated with the offer or sale of the
Shares or the Underlying Shares in a manner that would require the registration
under the Securities Act of the sale of the Shares or Underlying Shares to the
Purchaser.

           Section 4.6 Filing of Reports. For so long as the Company is subject
to the filing requirements of the Exchange Act, the Company shall timely file
with the SEC all reports required to be filed by it under the Exchange Act.

           Section 4.7 Furnishing of Rule 144A Materials. The Company shall, for
so long as any of the Shares or Underlying Shares remain outstanding and during
any period in which it is not subject to Section 13 or 15(d) of the Exchange
Act, make available to any registered holder of Shares or Underlying Shares in
connection with any sale thereof and any prospective purchaser

                                      -9-
<PAGE>   13
of such Shares or Underlying Shares from such Person, the following information
in accordance with Rule 144A(d)(4) under the Securities Act: a brief statement
of the nature of the business of the Company and the products and services it
offers and the Company's most recent audited balance sheet and profit and loss
and retained earnings statements, and similar audited financial statements for
such part of the two preceding fiscal years as the Company has been in
operation.

           Section 4.8 Solicitation Materials. The Company has not and shall not
solicit any offer to buy or sell the Shares or Underlying Shares by means of any
form of general solicitation or advertising.

           Section 4.9 Matters Affecting Purchaser's Rights. From the date
hereof through the Closing Date, the Company shall not and shall cause the
Subsidiaries not to, without the consent of the Purchaser, (i) amend its
Certificate of Incorporation, bylaws or other constituent documents so as to
adversely affect any rights of the Purchaser; (ii) split, combine or reclassify
its outstanding capital stock; (iii) other than the payment of a cash dividend,
declare, authorize, set aside or pay any dividend or other distribution with
respect to the Common Stock; or (iv) enter into any agreement with respect to
any of the foregoing.

           Section 4.10 HSR Act Filings. If a filing is required under the HSR
Act in connection with the issuance of the Shares or the Underlying Shares, the
Company shall, as expeditiously as possible, prepare and file, and shall
cooperate with the Purchaser in its preparation and filing of, any documents
required under the HSR Act.

                                    ARTICLE V

                         CONDITIONS PRECEDENT TO CLOSING

           Section 5.1 Conditions Precedent to Obligations of the Purchaser. The
obligation of the Purchaser to purchase the Shares is subject to the
satisfaction or waiver by the Purchaser, at or prior to the Closing, of each of
the following conditions:

               (a) Legal Opinion. The Purchaser shall have received the legal
opinion, addressed to it and dated the Closing Date, form the internal legal
counsel for the Company, substantially in the form of Exhibit B;

               (b) Accuracy of the Company's Representations and Warranties. The
representations and warranties of the Company contained herein shall be true and
correct as of the date when made and as of the Closing Date as though made at
that time (except that representations and warranties that are made as of a
specific date need be true only as of such date);

               (c) Performance by the Company. The Company shall have performed,
satisfied and complied in all material respects with all covenants, agreements
and conditions required by this Agreement to be performed, satisfied or complied
with by the Company at or prior to the Closing;

                                      -10-
<PAGE>   14
               (d) No Material Adverse Effect. Since the date of the financial
statements included in the Company's last filed Annual Report on Form 10-K, no
event which could reasonably be expected to have a Material Adverse Effect shall
have occurred;

               (e) No Prohibitions. The purchase of and payment for the Shares
(and upon conversion thereof, the Underlying Shares) hereunder shall not be
prohibited or enjoined (temporarily or permanently) by any applicable law or
governmental regulation;

               (f) Company Certificates. The Purchaser shall have received a
certificate substantially in the form of Exhibit C, dated the Closing Date,
signed by the Secretary or an Assistant Secretary of the Company and certifying
(i) that attached thereto is a true, correct and complete copy of (A) the
Company's Certificate of Incorporation, as amended to the date thereof and (B)
resolutions duly adopted by the Board of Directors of the Company, or committee
thereof, authorizing the execution and delivery of this Agreement and the
issuance and sale of the Shares and the Underlying Shares;

               (g) No Suspensions of Trading in Common Stock. Trading in the
Common Stock shall not have been suspended by the SEC or the NASD or other
exchange or market on which the Common Stock is listed or quoted (except for any
suspension of trading of limited duration solely to permit dissemination of
material information regarding the Company);

               (h) Delivery of Stock Certificates. The Company shall have
delivered to the Purchaser the stock certificate(s) representing the Shares,
registered in the name of the Purchaser;

               (i) Filing of Certificate of Designation. The Company shall have
filed with the Secretary of State of the State of Delaware, the Certificate of
Designation in the form attached hereto as Exhibit A;

               (j) Acquisition Agreement. The Company and the Purchaser shall
have entered into the Acquisition Agreement for the sale by the Company to the
Purchaser of a 20% undivided interest in certain of the assets and properties of
the Hawesville Aluminum Reduction Facility; and

               (k) Note Offering. Simultaneously with the Closing, the Company
shall have completed the offering of its Senior Secured First Mortgage Notes due
2008 and shall have consummated the acquisition of MetalsCo. and related assets.

           Section 5.2 Conditions Precedent to Obligations of the Company. The
obligation of the Company to issue and sell the Shares hereunder is subject to
the satisfaction or waiver by the Company, at or prior to the Closing, of each
of the following conditions:

               (a) Accuracy of the Purchaser's Representations and Warranties.
The representations and warranties of the Purchaser shall be true and correct as
of the date when made and as of the Closing Date as though made at that time
(except that representations and warranties that are made as of a specific date
need be true only as of such date);

                                      -11-
<PAGE>   15
               (b) No Prohibitions. The purchase of and payment for the Shares
(and upon conversion thereof, the Underlying Shares) hereunder shall not be
prohibited or enjoined (temporarily or permanently) by any applicable law or
governmental regulation;

               (c) Acquisition Agreement. The Purchaser and the Company shall
have entered into the Acquisition Agreement for the sale by the Company to the
Purchaser of a 20% undivided interest in certain of the assets and properties of
the Hawesville Aluminum Reduction Facility; and

               (d) Performance by the Purchaser. The Purchaser shall have
performed, satisfied and complied in all material respects with all covenants,
agreements and conditions required by this Agreement to be performed, satisfied
or complied with by it at or prior to the Closing.

                                   ARTICLE VI

                                   TERMINATION

           Section 6.1 Termination by Mutual Consent. This Agreement may be
terminated at any time prior to the Closing by the mutual consent of the Company
and the Purchaser.

           Section 6.2 Termination by the Company or the Purchaser. This
Agreement may be terminated prior to the Closing by either the Company or the
Purchaser, by giving written notice of such termination to the other party, if:

               (a) the Closing shall not have occurred by April 30, 2001;
provided that the terminating party is not then in material breach of its
obligations under this Agreement in any manner that shall have caused the
failure referred to in this paragraph (a);

               (b) there shall be in effect any statute, rule, law or regulation
that prohibits the consummation of the Closing or if the consummation of the
Closing would violate any non-appealable final judgment, order, decree, ruling
or injunction of any court of or governmental authority having competent
jurisdiction; or

               (c) there shall have been an amendment to the Securities Act or
the rules and regulations promulgated thereunder or an interpretive release
promulgated or issued thereunder, which, in the reasonable judgment of the
terminating party, would materially adversely affect or prohibit without
registration under the Securities Act the transactions contemplated hereby.

                                  ARTICLE VII

                                  MISCELLANEOUS

           Section 7.1 Fees and Expenses. The Company shall pay all stamp and
other similar taxes and duties levied in connection with the issuance of the
Shares (and upon conversion thereof, the Underlying Shares) pursuant hereto. The
Purchaser shall be responsible for its own tax liability that may arise as a
result of the investment hereunder or the transactions contemplated by this
Agreement. Whether or not the transactions contemplated by this

                                      -12-
<PAGE>   16
Agreement are consummated or this Agreement is terminated, the Company shall pay
(i) all costs, expenses, fees and all taxes incident to and in connection with:
(A) the preparation and filing of the Certificate of Designation and all
preliminary and final Blue Sky memoranda, (B) the issuance and delivery of the
Shares and the certificates for the Shares, and upon conversion thereof, the
Underlying Shares and the certificates for the Underlying Shares (including 50%
of all costs and expenses in connection with any filings required under the HSR
Act), and (C) furnishing such copies of the SEC Documents and all other
information filed with the SEC and all amendments and supplements thereto or the
information required to be delivered under Section 4.7 hereof, as the case may
be, as may reasonably be requested for use in connection with resales of the
Shares and, upon conversion thereof, the Underlying Shares, and (ii) all
reasonable fees and expenses of the counsel and accountants of the Purchaser
incurred by the Purchaser in connection with the negotiation, preparation,
execution and delivery of this Agreement.

           Section 7.2 Entire Agreement. This Agreement, together with the
Exhibits, hereto contains the entire understanding of the parties with respect
to the subject matter hereof and supersedes all prior agreements and
understandings, oral or written, with respect to such matters.

           Section 7.3 Notices. All notices, requests, demands and other
communications hereunder shall be in writing and shall be deemed given if
delivered personally or mailed by certified or registered mail, postage prepaid,
return receipt requested, or delivered to a nationally recognized next business
day courier for delivery on the next business day, or by facsimile, with a copy
sent as aforesaid and in any instance addressed as follows:

                     If to the Company:

                     Century Aluminum Company
                     2511 Garden Road
                     Building A Suite 200
                     Monterey, CA  93940
                     Fax:  831-642-9328
                     Attn:  Gerald J. Kitchen, Esq.

                     If to the Purchaser:

                     Glencore AG
                     Baarermattstrasse 3
                     P.O. Box 666
                     CH-6341 Baar
                     SWITZERLAND
                     Attn:  Chief Financial Officer

or such other address as may be designated in writing hereafter, in the same
manner, by such person.

                                      -13-
<PAGE>   17
           Section 7.4 Indemnification. The Company shall indemnify, defend and
hold harmless the Purchaser from and against all liabilities, losses, and
damages (with the exception of consequential, special, indirect and punitive
damages), together with all reasonable costs and expenses related thereto
(including, without limitation, reasonable legal and accounting fees and
expenses), which arise out of, result from or relate to any misrepresentation or
breach by the Company of, or any failure by the Company to perform, any of its
representations, warranties, covenants, obligations or agreements in this
Agreement, the Certificate of Designation or any other instrument furnished by,
or on behalf of, the Company under this Agreement. Notwithstanding anything to
the contrary contained in this Section 7.4, the Company's liability under this
Section shall not exceed US$25,000,000 plus the reasonable costs and expenses
incurred by the Purchaser under this Section 7.4.

           Section 7.5 Arbitration. All controversies, claims, differences or
disputes arising under, relating to or connected with this Agreement shall be
finally settled by arbitration in accordance with the Commercial Arbitration
Rules of the American Arbitration Association (the "AAA Rules"). The parties
agree that such arbitration (i) shall take place in New York, New York, U.S.A.,
(ii) shall be before a panel of three (3) arbitrators chosen in accordance with
the AAA Rules, and (iii) shall be conducted in the English language. The award
in any such arbitration shall be final, binding and conclusive; and judgment
thereon may be entered in any court of competent jurisdiction.

           Section 7.6 Amendments; Waivers. No provision of this Agreement may
be waived or amended except in a written instrument signed, in the case of an
amendment, by both the Company and the Purchaser, or, in the case of a waiver,
by the party against whom enforcement of any such waiver is sought. No waiver of
any default with respect to any provision, condition or requirement of this
Agreement shall be deemed to be a continuing waiver in the future or a waiver of
any other provision, condition or requirement hereof, nor shall any delay or
omission of either party to exercise any right hereunder in any manner impair
the exercise of any such right accruing to it thereafter.

           Section 7.7 Headings. The headings herein are for convenience only,
do not constitute a part of this Agreement and shall not be deemed to limit or
affect any of the provisions hereof.

           Section 7.8 Successors and Assigns. This Agreement shall be binding
upon and inure to the benefit of the parties and their successors and permitted
assigns, including each other Person who shall become a registered holder of the
Shares or the Underlying Shares transferred to such holder by the Purchaser or
its permitted transferees and their respective legal representatives, successors
and assigns. The Company shall not assign this Agreement or any rights or
obligations hereunder without the prior written consent of the Purchaser.

           Section 7.9 No Third Party Beneficiaries. This Agreement is intended
for the benefit of the parties hereto and their respective permitted successors
and assigns and is not for the benefit of, nor may any provision hereof be
enforced by, any other Person.

           Section 7.10 Governing Law. This Agreement shall be governed by and
construed and enforced in accordance with the internal laws of the State of
Delaware without regard to the principles of conflicts of law thereof.

                                      -14-
<PAGE>   18
           Section 7.11 Survival. The representations and warranties of the
Company and the Purchaser contained in Article III and the agreements and
covenants of the parties contained in Article IV and this Article VII shall
survive the Closing (or any earlier termination of this Agreement) and any
conversion or transfer of the Shares hereunder.

           Section 7.12 Counterpart Signatures. This Agreement may be executed
in two or more counterparts, all of which when taken together shall be
considered one and the same agreement and shall become effective when
counterparts have been signed by each party and delivered to the other party, it
being understood that both parties need not sign the same counterpart. In the
event that any signature is delivered by facsimile transmission, such signature
shall create a valid and binding obligation of the party executing (or on whose
behalf such signature is executed) the same with the same force and effect as if
such facsimile signature page were an original thereof.

           Section 7.13 Publicity. The Company and the Purchaser shall consult
with each other in issuing any press releases or otherwise making public
statements with respect to the transactions contemplated hereby and neither
party shall issue any such press release or otherwise make any such public
statement without the prior written consent of the other, which consent shall
not be unreasonably withheld or delayed, unless such press release or public
statement is required by law, in which case, the parties shall consult with each
other to the extent practical under the circumstances regarding the text of such
press release or public statement.

           Section 7.14 Severability. In case any one or more of the provisions
of this Agreement shall be invalid or unenforceable in any respect, the validity
and enforceability of the remaining terms and provisions of this Agreement shall
not in any way be affected or impaired thereby and the parties will attempt to
agree upon a valid and enforceable provision which shall be a reasonable
substitute therefor, and upon so agreeing, shall incorporate such substitute
provision in this Agreement.

           Section 7.15 Remedies. In addition to being entitled to exercise all
rights provided herein or granted by law, including recovery of damages, the
Purchaser will be entitled to specific performance of the obligations of the
Company under this Agreement and the Company will be entitled to specific
performance of the obligations of the Purchaser hereunder. Each of the Company
and the Purchaser agrees that monetary damages would not be adequate
compensation for any loss incurred by reason of any breach of its obligations
described in the foregoing sentence and hereby agrees to waive in any action for
specific performance of any such obligation the defense that a remedy at law
would be adequate.

           IN WITNESS WHEREOF, the parties have executed this Agreement as of
the date first written above.

                                        CENTURY ALUMINUM COMPANY

                                        By:        /s/ Gerald J. Kitchen
                                             ----------------------------------
                                                   Name:  Gerald J. Kitchen
                                                   Title: Executive Vice
                                                          President, General
                                                          Counsel and Chief
                                                          Administrative Officer

                                      -15-
<PAGE>   19
GLENCORE AG

By:     /s/ Josef Bermann              Zbynek Zak
       ------------------------------------------
Name:   Josef Bermann                  Zbynek Zak
Title:  Director                       Director

                                      -16-

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