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                                                                     Exhibit 3.6

                            Certificate of Amendment

                                       of

                          Certificate of Incorporation

                                       of

                                Clark USA, Inc.



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

                   Adopted in accordance with the provisions
                   of Section 242 of the General Corporation
                          Law of the State of Delaware

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


     I, Maura Clark, Executive Vice President of CLARK USA, INC., a corporation
organized and existing under the laws of the State of Delaware (the
"Corporation"), hereby certify as follows:

     FIRST:  That the Restated Certificate of Incorporation of the Corporation
was filed with the Secretary of State of the State of Delaware on the 28th day
of December, 1994 and that Certificates of Amendment thereto were filed with the
Secretary of State of the State of Delaware on the 23rd day of February, 1995,
the 3rd day of November, 1995 and on two occasions on the 1st day of October,
1997 (as so amended, the "Certificate of Incorporation").

     SECOND:  That Article 4 of the Certificate of Incorporation of the
Corporation has been amended to read in its entirety as follows:
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     ARTICLE 4.  The total number of shares of capital stock which the
Corporation shall have the authority to issue is 68,554,552 shares, consisting
of (a) 63,554,552 shares of common stock, par value $.0l per share, of which (i)
54,164,597 shares shall be designated "Common Stock," (ii) 3,389,955 shares
shall be designated "Class D Common Stock," and (iii) 6,000,000 shares shall be
designated "Class F Common Stock", and (b) 5,000,000 shares of "Preferred
Stock," par value $.01 per share.

A.  Preferred Stock.

     1.  Issuance.  The Board of Directors is authorized, subject to limitations
prescribed by law, to provide for the issuance of shares of Preferred Stock in
one or more Classes to establish the number of shares to be included in each
such Class, and to fix the designations, powers, preferences and rights of the
shares of each such Class, and any qualifications, limitations or restrictions
thereof.

B.  Common Stock.

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Common Stock shall be entitled to receive, when,
as and if declared by the Board of Directors, out of the assets of the
Corporation which are by law available therefor, dividends payable either in
cash, in property or in shares of capital stock.  The Board of Directors may not
declare or pay any dividend or distribution with respect to the Common Stock
unless the same dividend or distribution per share has been declared or paid, as
the case may be, with respect to the Class D Common Stock and the Class F Common
Stock; provided, that with respect to dividends payable only in shares of common
stock, each of the Common Stock, the Class D Common Stock and the Class F Common
Stock shall receive an equivalent dividend per share payable in common stock of
the corresponding class.

     2.  Voting Rights.  At every annual or special meeting of stockholders of
the Corporation, every share of Common Stock shall entitle the holder thereof to
one vote, voting together with the holders of Class F Common Stock, in person or
by proxy, for each share of Common Stock standing in his or her name on the
books of the Corporation; provided that the holders of Common Stock shall have
no voting rights with respect to matters reserved (by law or by agreement with
the Corporation) solely for any other class of capital stock.

     3.  Liquidation, Dissolution or Winding Up.  In the event of any voluntary
or involuntary liquidation, dissolution or winding up of the affairs of the
Corporation (a "Liquidation"), after payment or provision for payment of the
debts and other liabilities of the Corporation and of the preferential amounts,
if any, to which the holders of Preferred Stock shall be entitled, the holders
of all outstanding shares of Common Stock shall be entitled to share ratably, on
a share-for-share basis, with the holders of Class D Common Stock and Class F
Common Stock in the remaining assets of the Corporation.

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C.  Class D Common Stock

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Class D Common Stock shall be entitled to
receive the same dividends or distributions per share, whether payable in cash,
in property or in shares of capital stock, as may be declared and paid on the
Common Stock and the Class F Common Stock, and the Board of Directors may not
declare or pay any dividend or distribution with respect to the Class D Common
Stock unless the same dividend or distribution per share has been declared or
paid, as the case may be, with respect to the Common Stock and the Class F
Common Stock; provided, that with respect to dividends payable only in shares of
common stock, each of the Common Stock, the Class D Common Stock and the Class F
Common Stock shall receive an equivalent dividend per share payable in common
stock of the corresponding class.

     2.  Voting Rights.  Holders of shares of Class D Common Stock shall not be
accorded any voting rights in respect thereof and such shares shall not be
deemed to be outstanding for purposes of determining the vote required on any
matter properly brought before the stockholders of the Corporation for a vote
thereon.

     3.  Conversion.  (a)  The Company shall have the right, at any time and
from time to time, to convert any or all of the shares of Class D Common Stock
into an equal number of shares of Common Stock.  The method of selection of such
shares shall be determined by the Board of Directors of the Company in its sole
discretion.

          (b) Following an initial public offering of Common Stock, any person
who is not an affiliate of Occidental Petroleum Corporation to whom shares of
Class D Common Stock have been directly or indirectly transferred by Occidental
Petroleum Corporation in an arm's-length transaction shall have the right, at
any time and from time to time, to convert any or all of such shares of Class D
Common Stock into an equal number of shares of Common Stock.

          (c) Following an initial public offering of Common Stock, any person
who is not an affiliate of Gulf Resources Corporation to whom shares of Class D
Common Stock have been directly or indirectly transferred by Gulf Resources
Corporation in an arm's-length transaction shall have the right, at any time and
from time to time, to convert any or all of such shares of Class D Common Stock
into an equal number of shares of Common Stock.

     4.  Liquidation, Dissolution or Winding Up.  In the event of any voluntary
or involuntary liquidation, dissolution or winding up of the affairs of the
Corporation (a "Liquidation"), after payment or provision for payment of the
debts and other liabilities of the Corporation and of the preferential amounts,
if any, to which the holders of Preferred Stock shall be entitled, the holders
of all outstanding shares of Class D Common Stock shall be entitled to share
ratably, on a share-for-share basis, with the holders of Common Stock and Class
F Common Stock in the remaining assets of the Corporation.

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     5.  Anti-Dilution.  In the event the Company shall at any time (a) declare
a dividend on any shares of capital stock of the Company or any securities
issued in respect thereof, or in substitution therefor, in connection with any
stock split, dividend or combination, or any recapitalization, merger,
consolidation, exchange or other similar reorganization (a "Recapitalization"),
such dividend being payable in shares of capital stock of the Company, (b)
subdivide the outstanding capital stock of the Company, (c) combine the
outstanding capital stock of the Company into a smaller number of shares, or (d)
issue any shares of capital stock in a Recapitalization, the number of shares of
Class D Common Stock then outstanding shall be proportionately adjusted so that
the relative equity percentage ownership of the Company and the relative voting
power represented by each such share shall be preserved as nearly as
practicable.

D.  Class F Common Stock.

     1.  Dividends.  Subject to the preferential rights, if any, of the
Preferred Stock, the holders of Class F Common Stock shall be entitled to
receive the same dividends or distributions per share, whether payable in cash,
in property or in shares of capital stock, as may be declared and paid on the
Common Stock and Class D Common Stock, and the Board of Directors may not
declare or pay any dividend or distribution with respect to the Class F Common
Stock unless the same dividend or distribution per share has been declared or
paid, as the case may be, with respect to the Common Stock and Class D Common
Stock; provided, that with respect to dividends payable only in shares of common
stock, each of the Common Stock, the Class D Common Stock and the Class F Common
Stock shall receive an equivalent dividend per share payable in common stock of
the corresponding class.

     2.  Voting Rights.  At every annual or special meeting of stockholders of
the Corporation, every share of Class F Common Stock shall entitle the holder
thereof to one vote (subject to adjustment as provided below), voting together
with the holders of Common Stock, on all matters submitted to a vote of the
holders of Common Stock or Class F Common Stock, in person or by proxy, in the
same manner and with same effect as the holders of Common Stock; provided that
the holders of Class F Common Stock shall have no voting rights with respect to
matters reserved (by law or by agreement with the Corporation) solely for any
other class of capital stock; and provided further, that if the holders of the
Class F Common Stock would otherwise be entitled to cast votes representing, in
the aggregate, more than 19.9% of the total voting power of all classes of
capital stock of the Corporation entitled to vote, then the vote allotted to
each share of Class F Common Stock shall be proportionately reduced so that all
outstanding shares of Class F Common Stock shall be entitled to cast votes
representing, in the aggregate, 19.9% of the total voting power of all classes
of capital stock of the Corporation entitled to vote.

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     3.  Conversion.  Any shares of Class F Common Stock that are owned
beneficially or of record by Occidental Petroleum Corporation and its affiliates
shall have no conversion rights.  Any holder of any shares of Class F Common
Stock other than Occidental Petroleum Corporation and its affiliates shall have
the right, at any time and from time to time, to convert any or all of such
other holder's shares of Class F Common Stock into an equal number of shares of
Common Stock.

     4.  Antidilution.  In the event the Corporation shall at any time (a)
declare a dividend on any shares of capital stock of the Corporation or any
securities issued in respect thereof, or in substitution therefor, such dividend
being payable in shares of capital stock of the Corporation, (b) subdivide the
outstanding capital stock of the Corporation, or (c) combine the outstanding
capital stock of the Corporation into a smaller number of shares, the provisions
relating to the conversion of shares of Class F Common Stock into Common Stock
shall be equitably and proportionately adjusted.

     5.  Liquidation, Dissolution or Winding Up.  In the event of any
Liquidation, after payment or provision for payment of the debts and other
liabilities of the Corporation and of the preferential amounts, if any, to which
the holders of Preferred Stock shall be entitled, the holders of all outstanding
shares of Class F Common Stock shall be entitled to share ratably, on a share-
for-share basis, with the holders of Common Stock and Class D Common Stock in
the remaining assets of the Corporation.

D.  Reclassification.  All shares of Class F Common Stock issued and outstanding
immediately prior to the filing of this Certificate of Amendment with the
Secretary of State of the State of Delaware are hereby reclassified and, without
any further action on the part of the Corporation or the holder of such shares,
shall hereafter be deemed to have become an aggregate of 63,000 shares of
Preferred Stock known as "Exchangeable Preferred Stock," the terms of which
shall be set forth in the Certificate of Designations with respect to the
Exchangeable Preferred Stock in the form of Exhibit A hereto.

E.  Amendment of this Article.  The Corporation may not amend, alter, change or
repeal in any manner adverse to the holders of the Class D Common Stock or the
Class F Common Stock the rights or preferences of the holders of the Class D
Common Stock or the Class F Common Stock contained in this Article 4 without the
consent of the holders of 95% of the Class D Common Stock or the Class F Common
Stock, as the case may be.

     THIRD:  That such amendment has been duly adopted in accordance with the
provisions of the General Corporation Law of the State of Delaware by the
written consent of the holders of a majority of outstanding shares of each class
entitled to vote thereon in accordance with the provisions of Section 228 of the
General Corporation Law.

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     IN WITNESS WHEREOF, the undersigned has signed this Certificate this 1st
day of October, 1997.

                              CLARK USA, INC.
                              By:     /s/  Maura J. Clark
                                 ------------------------
                              Name:  Maura J. Clark
                              Title: Executive Vice President &
                                     Chief Financial Officer



Attested By:


/s/  Katherine D. Knocke
--------------------------
Name:  Katherine D. Knocke
Title: Secretary

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