<PAGE>

                                                                    EXHIBIT 10.1

                                                                  EXECUTION COPY

                                WAIVER LETTER AND
                                 AMENDMENT NO. 6
                                       TO
                                CREDIT AGREEMENT

        This WAIVER LETTER AND AMENDMENT NO. 6 TO CREDIT AGREEMENT (this
"Agreement and Amendment"), made as of March 31, 2003, among OGLEBAY NORTON
COMPANY ("Borrower"), the banking institutions named in Schedule 1 to the Credit
Agreement (as hereinafter defined) (collectively, the "Banks" and individually,
"Bank"), KEYBANK NATIONAL ASSOCIATION, as administrative agent for the Banks
("Agent"), BANK ONE, MICHIGAN (now known as Bank One, NA), as syndication agent
("Syndication Agent") and THE BANK OF NOVA SCOTIA, as documentation agent
("Documentation Agent").

                                   WITNESSETH:

        WHEREAS, Borrower, the Banks, Agent, the Syndication Agent and the
Documentation Agent have entered into that certain Credit Agreement, dated as of
May 15, 1998, as amended and restated as of April 3, 2000, and as subsequently
amended by that certain Amendment No. 1 to Credit Agreement and Waiver, dated as
of June 30, 2001, Amendment No. 2 to Credit Agreement and Waiver, dated as of
November 9, 2001, Amendment No. 3 to Credit Agreement, dated as of December 24,
2001, Amendment No. 4 to Credit Agreement, dated as of October 23, 2002, and
Amendment No. 5 to Credit Agreement, dated as of January 8, 2003 (as so amended
from time to time, the "Credit Agreement"), pursuant to which the Banks have
made certain loans and other financial accommodations available to Borrower;

        WHEREAS, Borrower has advised the Agent that Borrower may violate one or
more of the financial covenants contained in Section 5.7 of the Credit Agreement
as of and for the period ending March 31, 2003 (the "Financial Covenant
Violations");

        WHEREAS, subject to the terms and conditions hereof, the Banks and the
Agent are willing to temporarily waive: (i) the Events of Default set forth in
Section 7.2 (the "Designated Events of Default") of the Credit Agreement which
will occur by reason of the Financial Covenant Violations and (ii) the exercise
of rights and remedies under the Credit Agreement with respect to such
Designated Events of Default; and

        WHEREAS, the parties also desire to amend certain provisions of the
Credit Agreement as set forth herein and the Banks which are signatories hereto
constitute the "Majority Banks" required to so amend the Credit Agreement
pursuant to Section 10.3 thereof;

        NOW, THEREFORE, in consideration of the mutual promises and agreements
contained herein and other good and valuable consideration, the receipt and
adequacy of which are hereby acknowledged, Borrower and the Banks hereby agree
as follows:

<PAGE>

1.      DEFINED TERMS.

        Each defined term used herein and not otherwise defined herein shall
have the meaning ascribed to such term in the Credit Agreement, as amended
hereby.

2.      AGREEMENT TO WAIVE.

        Notwithstanding the occurrence or continuation of the Designated Events
of Default, subject to satisfaction of the conditions precedent set forth in
Section 5 hereof, the Designated Events of Default are hereby waived in
accordance with the Credit Agreement from the date of occurrence thereof until
and including June 15, 2003 (the "Waiver Expiration Date") and the Banks and the
Agent will not exercise rights and remedies under the Credit Agreement and the
other Loan Documents as a result of the occurrence of such Designated Events of
Default until after the Waiver Expiration Date. Nothing contained in this
Agreement and Amendment shall prejudice any rights or remedies the Banks or the
Agent may have, or the right of the Banks and the Agent to exercise any such
rights and remedies, prior to the Waiver Expiration Date with respect to Events
of Default (whether now existing or hereafter occurring and including any
violation of Section 5.7A) other than the Designated Events of Default.
Moreover, nothing contained in this Agreement and Amendment shall prejudice any
rights or remedies the Banks or the Agent may have, or the right of the Banks or
the Agent to exercise any such rights and remedies, with respect to any Events
of Default (including the Designated Events of Default) after the Waiver
Expiration Date. The obligations of the Banks shall be governed only by, and
shall remain subject only to, the terms of the Credit Agreement and the other
Loan Documents except that, by reason of the execution of this Agreement and
Amendment, the Designated Events of Default shall not, prior to the Waiver
Expiration Date, limit Borrower's ability to obtain Loans and Letters of Credit
otherwise available under the Credit Agreement.

3.      AMENDMENT TO THE CREDIT AGREEMENT.

        3.1     Amendment to Article I. Article I, Definitions, is amended as
follows: (x) new definition "Amendment No. 6 Closing Date," shall be added to
Article I and inserted therein in appropriate alphabetical order, to read as set
forth below and (y) paragraph (a) of the definition of "Applicable Margin" and
the first clause of paragraph (b) of such definition shall each be amended to
read as set forth below:

        "Amendment No. 6 Closing Date" shall mean date on which the "Effective
Date" (as such term is defined in Section 5 of that certain Waiver Letter and
Amendment No. 6 to Credit Agreement, dated as of March 31, 2003) occurs.

        "Applicable Margin" shall mean:

                (a)     for the period commencing on the Amendment No. 6 Closing
        Date until and including August 15, 2003, (i) four hundred fifty (450)
        basis points for LIBOR Loans, and (ii) two hundred twenty (225) basis
        points for Prime Rate Loans, and . . .

                (b)     commencing August 16, 2003, . . .

        3.2     Amendment to Section 5.3. Section 5.3 of the Credit Agreement is
hereby amended as follows: (w) with respect to fiscal quarter ending March 31,
2003 only, paragraph (a) of Section 5.3 shall be amended so that financial
statements with respect to such fiscal quarter shall be required to be released
to the public and delivered to each Bank on May 1, 2003 and such financial
statements with respect to such fiscal quarter (with any adjustments made to
such

                                        2
                       Amendment No.6 to Credit Agreement

<PAGE>

financial statements) shall be disclosed in the Borrower's 10Q and delivered to
each Bank by May 15, 2003, (x) with respect to fiscal quarter ending March 31,
2003 only, paragraph (c) of Section 5.3 shall be amended so that the Borrower
shall be required to deliver to each Bank on May 1, 2003 calculations of the
financial covenants set forth in Section 5.7A (rather than Section 5.7) of the
Credit Agreement which calculations shall be based on the financial statements
delivered to the Banks on May 1, 2003 and certified by a Financial Officer of
the Borrower (subject to such adjustments as are made to the financial
statements included in the 10Q filed for March 31, 2003), (y) with respect to
fiscal quarter ending March 31, 2003 only, paragraph (c) of Section 5.3 shall be
further amended so that the Borrower shall be required to deliver to each Bank
on May 15, 2003 a Compliance Certificate and calculations of the financial
covenants set forth in Section 5.7A (rather than Section 5.7) of the Credit
Agreement which calculations shall be based on the financial statements
delivered to the Banks on May 15, 2003 and certified by a Financial Officer of
the Borrower, (z) paragraph (g) thereof shall be amended to delete the word
"and" following such paragraph (g) and to add the word "and" after paragraph (h)
thereof and (zz) new paragraph (i) shall be added to Section 5.3 to read as set
forth below:

                (i)     On or prior to May 30, 2003, a comprehensive business
        plan for fiscal years 2003 and 2004, the form, detail and substance of
        which shall be satisfactory to the Agent and the Banks.

        3.3     Temporary Financial Covenants. From and after the Amendment No.
6 Closing Date until and including the Waiver Expiration Date, Section 5 of the
Credit Agreement shall be amended to add Section 5.7A to read as set forth below
(the terms of Section 5.7 as in effect prior to this Agreement and Amendment
shall become again effective on and after June 16, 2003):

        SECTION 5.7     TEMPORARY FINANCIAL COVENANTS

                (a)     LEVERAGE RATIO. The Companies shall not suffer or permit
        at any time the Leverage Ratio to exceed 6.90 to 1.00 on March 31, 2003
        through and including June 15, 2003.

                (b)     SENIOR SECURED DEBT RATIO. The Companies shall not
        suffer or permit at any time the ratio of: (x) Total Senior Funded
        Indebtedness to the extent such Indebtedness is a secured obligation
        (but, excluding for purposes hereof, the Indebtedness evidenced by the
        2002 Senior Secured Fund Notes) to (y) Consolidated Pro-Forma EBITDA to
        be greater than 4.05 to 1.00 on March 31, 2003 through and including
        June 15, 2003, based upon the financial statements of the Companies for
        the most recently completed four (4) fiscal quarters.

                (c)     INTEREST COVERAGE. The Companies shall not suffer or
        permit at any time the ratio of: (x) Consolidated Pro-Forma EBITDA to
        (y) Consolidated Pro-Forma Interest Expense (less non cash amortized
        financing and FAS 133 costs to the extent included in Consolidated
        Pro-Forma Interest Expense in accordance with GAAP) to be less than 1.40
        to 1.00 on March 31, 2003 through and including June 15, 2003, based
        upon the financial statements of the Companies for the most recently
        completed four (4) fiscal quarters.

                (d)     CASH-FLOW COVERAGE. The Companies shall not suffer or
        permit at any time the ratio of: (x) Consolidated Pro-Forma Cash Flow to
        (y) Consolidated Pro-Forma

                                        3
                       Amendment No.6 to Credit Agreement

<PAGE>

        Fixed Charges (excluding from Pro-Forma Fixed Charges for purposes of
        calculating compliance with this covenant, amounts payable with respect
        to the Revolving Loans and the Term Loans (as defined in the Loan
        Agreement) to be less than 0.90 to 1.00 on March 31, 2003 through and
        including June 15, 2003, based upon the financial statements of the
        Companies for the most recently completed four (4) fiscal quarters.

                (e)     NET WORTH. The Companies shall not suffer or permit
        Consolidated Net Worth at any time, based upon the Consolidated
        financial statements of the Companies for the most recently completed
        fiscal quarter, to fall below the current minimum amount required, which
        current minimum amount required shall be as of March 31, 2003, an amount
        equal to $98,643,000; provided, however, that (i) any non-cash impact to
        Consolidated Net Worth related to FAS 142 shall be excluded in
        calculating Borrower's compliance with this covenant and (ii) any
        potential non-cash impact associated with the extinguishment of
        Indebtedness (as a result of the issuance of the 2002 Senior Secured
        Fund Notes and the required repayment of a portion of the Revolving
        Credit Loans) as indicated pursuant to EITF 96.19/SFAS 140 shall
        likewise be excluded in calculating Borrower's compliance with this
        covenant.

                (f)     MINIMUM CONSOLIDATED PRO-FORMA EBITDA. The Companies
        shall not suffer or permit at any time Consolidated Pro-Forma EBITDA to
        be less than $62,500,000 on March 31, 2003 through and including June
        15, 2003, based upon the financial statements of the Companies for the
        most recently completed four (4) fiscal quarters.

                (g)     Minimum Revolving Credit Availability. The Companies
        shall at all times maintain a Revolving Credit Availability of not less
        than $3,500,000 on March 31, 2003 through and including June 15, 2003.

        3.4     Amendment to Section 7.2. Section 7.2 of the Credit Agreement is
hereby amended to add therein a reference to "5.7A" after the reference to
"5.7".

4.      REPRESENTATIONS AND WARRANTIES.

        Borrower hereby represents and warrants as follows:

        4.1     The Agreement and Amendment. This Agreement and Amendment has
been duly and validly executed by an authorized executive officer of Borrower
and constitutes the legal, valid and binding obligation of Borrower enforceable
against Borrower in accordance with its terms. The execution, delivery, and
performance of this Agreement and Amendment, the Credit Agreement (as amended
hereby), and the other Loan Documents to which Borrower is a party are within
Borrower's corporate powers, have been duly authorized, and are not in
contravention of Law or the terms of Borrower's Certificate of Incorporation or
By-Laws or any indenture (including the Indenture) or other document or
instrument evidencing borrowed money or any other agreement or undertaking to
which Borrower is a party or by which it or its property is bound.

        4.2     Claims and Defenses. As of the date of this Agreement and
Amendment, neither Borrower nor any of the Companies has any defenses, claims,
counterclaims or setoffs with respect to the Credit Agreement, the Loan
Documents or any obligations thereunder or with respect to any actions of Agent,
the Syndication Agent, the Documentation Agent, the Banks or

                                        4
                       Amendment No.6 to Credit Agreement

<PAGE>

any of their respective officers, directors, shareholders, employees, agents or
attorneys, and Borrower irrevocably and absolutely waives any such defenses,
claims, counterclaims and setoffs and releases Agent, the Syndication Agent, the
Documentation Agent, the Banks, and each of their respective officers,
directors, shareholders, employees, agents and attorneys, from the same.

        4.3     Credit Agreement; Status of Credit Agreement. The Credit
Agreement, as amended by this Agreement and Amendment, remains in full force and
effect and remains the valid and binding obligation of Borrower enforceable
against Borrower in accordance with its terms except as expressly limited
hereby. As of the date of this Agreement and Amendment, the representations and
warranties of Borrower set forth in the Credit Agreement are true and correct
with the same force and effect as if made on and as of such date except to the
extent that any thereof expressly relate to an earlier date.

        4.4     Nonwaiver. The execution, delivery, performance and
effectiveness of this Agreement and Amendment shall not, except as provided in
Article 2 of this Agreement and Amendment, operate, be deemed to be, or be
construed to be a waiver: (i) of any right, power or remedy of Agent, the
Syndication Agent, the Documentation Agent, or any Bank under the Credit
Agreement or (ii) of any term, provision, representation, warranty or covenant
contained in the Credit Agreement or any other documentation executed in
connection therewith. Further, except as provided in Article 2 of this Agreement
and Amendment, none of the provisions of this Agreement and Amendment shall
constitute, be deemed to be or construed to be: (i) a waiver of any Event of
Default under the Credit Agreement as previously amended and as further amended
by this Agreement and Amendment or (ii) a revocation of any prior written
waivers of any Events of Default thereunder.

        4.5     Reference to and Effect on the Credit Agreement. Upon the
effectiveness of this Agreement and Amendment, each reference in the Credit
Agreement to "this Agreement," "hereunder," "hereof," "herein," or words of like
import shall mean and be a reference to the Credit Agreement, as previously
amended and as further amended hereby, and each reference to the Credit
Agreement in any other document, instrument or agreement executed and/or
delivered in connection with the Credit Agreement shall mean and be a reference
to the Credit Agreement, as previously amended and as further amended hereby.

5.      CONDITIONS PRECEDENT TO EFFECTIVENESS OF THIS AGREEMENT AND AMENDMENT.

        This Agreement and Amendment shall become effective as of the time (the
"Effective Date") on which each of the following conditions precedent shall have
been fulfilled:

        5.1     Waiver Letter and Amendment No. 6 to Credit Agreement. Agent
shall have received from Borrower and Banks constituting Majority Banks (as
determined by the Agent) an original counterpart of this Agreement and
Amendment, executed and delivered by a duly authorized officer of Borrower and
each such Bank, as the case may be.

        5.2     Waiver Letter and Amendment No. 6 to Loan Agreement. Agent shall
have received from Borrower and Banks constituting Majority Banks an original
counterpart of the Waiver Letter and Amendment No. 6 to Loan Agreement, in form
and substance acceptable to Agent, executed and delivered by a duly authorized
officer of Borrower and each such Bank, as the case may be.

                                        5
                       Amendment No.6 to Credit Agreement

<PAGE>

        5.3     Acknowledgment of Guarantors. Agent shall have received the
Acknowledgment of Guarantors, attached hereto, executed and delivered by a duly
authorized officer of each of the Guarantors.

        5.4     Independent Business Consultant. An independent business
consultant, which has a recognized reputation for working with financial
situations comparable to Borrower's and with industries consistent with
Borrower's industry segments and which is otherwise acceptable to the Agent as a
matter of sound credit policy, shall have been retained by Borrower pursuant to
a written engagement the form, scope and substance of which shall be
satisfactory to the Agent.

        5.5     Agreement and Amendment Fee. Agent shall have received, for the
benefit of each Bank (including Agent in its capacity as a Bank) approving and
executing both this Agreement and Amendment and the Waiver Letter and Amendment
No. 6 to Loan Agreement, a one time fee in the amount of ten (10.00) basis
points multiplied by the sum of the Revolving Credit Commitment of such Bank
plus the Term Loan Commitment Amount (as defined in the Loan Agreement) of such
Bank.

        5.6     Opinion Concerning Agreement and Amendment. Agent shall have
received an opinion of counsel to Borrower and its subsidiaries, in form and
substance satisfactory to the Agent, as to the authorization, due execution and
delivery, and enforceability by and against Borrower and the Subsidiaries
thereof which are parties to this Agreement and Amendment.

6.      MISCELLANEOUS.

        6.1     Governing Law. This Agreement and Amendment has been delivered
and accepted at and shall be deemed to have been made at Cleveland, Ohio. This
Agreement and Amendment shall be interpreted and the rights and liabilities of
the parties hereto determined in accordance with the laws of the State of Ohio,
without regard to principles of conflict of law, and all other laws of mandatory
application.

        6.2     Severability. Each provision of this Agreement and Amendment
shall be interpreted in such manner as to be valid under applicable law, but if
any provision hereof shall be invalid under applicable law, such provision shall
be ineffective to the extent of such invalidity, without invalidating the
remainder of such provision or the remaining provisions hereof.

        6.3     Counterparts. This Agreement and Amendment may be executed in
one or more counterparts, each of which, when taken together, shall constitute
but one and the same agreement.

                           [Signature Page to Follow]

                                        6
                       Amendment No.6 to Credit Agreement

<PAGE>

        IN WITNESS WHEREOF, Borrower has caused this Waiver Letter and Amendment
No. 6 to Credit Agreement to be duly executed and delivered by its duly
authorized officer as of the date first above written.

Address:    North Point Tower                OGLEBAY NORTON COMPANY
            1001 Lakeside Avenue,            By:
            15th floor                           -------------------------------
            Cleveland, Ohio 44114-1151       Name:  Julie A. Boland
            Attention:  Treasurer                  -----------------------------
                                             Title: Chief Financial Officer
                                                   -----------------------------


Address:    Key Center                       KEYBANK NATIONAL ASSOCIATION,
            127 Public Square                as a Bank and as Agent
            Cleveland, Ohio  44114-1306
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:  Thomas J. Purcell
                                                  ------------------------------
                                             Title: Sr. Vice President
                                                   -----------------------------


Address:    611 Woodward Avenue              BANK ONE, NA (formerly known as
            Detroit, Michigan  48226         One, Michigan) Bank
            Attention:  Large Corporate
            Banking Division                 By:
                                                --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    600 Peachtree Street             THE BANK OF NOVA SCOTIA
            Suite 2700
            Atlanta, Georgia  30308          By:
            Attention:  Large Corporate         --------------------------------
            Banking Division                 Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------

                                       S-1
                       Amendment No.6 to Credit Agreement

<PAGE>

Address:    500 Woodward Avenue, 9th Fl.     COMERICA BANK
            Detroit, Michigan 48226
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------

Address:    231 S. LaSalle Street            BANK OF AMERICA, N.A.
            Chicago, Illinois 60697
            Attention:  Ronald A. Prince     By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    111 West Monroe, 10W             HARRIS TRUST AND SAVINGS BANK
            Chicago, Illinois  60603
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    975 Euclid Avenue                THE HUNTINGTON NATIONAL BANK
            Cleveland, Ohio  44115
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    6 High Ridge Park                GE CAPITAL CFE, INC.
            Building 6C, Mail Stop 4097-203
            Stamford Ct, 06927-5100          By:
            Attention:  Commercial Finance      --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    1900 East Ninth Street           NATIONAL CITY BANK
            Cleveland, Ohio  44114
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    250 West Huron                   JPMORGAN CHASE BANK
            Cleveland, Ohio  44113
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------

                                       S-2
                       Amendment No.6 to Credit Agreement

<PAGE>

Address:    1404 East Ninth Street           FIFTH THIRD BANK
            Cleveland, Ohio  44114
            Attention:  Large Corporate      By:
            Banking Division                    --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    1350 Euclid Avenue               U. S. BANK, NATIONAL ASSOCIATION
            Cleveland, Ohio                  (f\k\a Firstar Bank National
            Attention: Commercial            Association)
            Banking Division                 By:
                                                --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    1185 Avenue of the Americas      FLEET NATIONAL BANK
            New York, New York 10036
            Attention:  Manhattan            By:
            Commercial                          --------------------------------
                                             Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------


Address:    110 South Stratford Road         BRANCH BANKING & TRUST CO.
            Suite 301
            Winston-Salem, NC 27104          By:
            Attention:  Large Corporate         --------------------------------
            Banking Division                 Name:
                                                  ------------------------------
                                             Title:
                                                   -----------------------------

                                       S-3
                       Amendment No.6 to Credit Agreement

<PAGE>

                          ACKNOWLEDGMENT OF GUARANTORS

        Each of the undersigned consents and agrees to and acknowledges the
terms of the foregoing Waiver Letter and Amendment No. 6 to Credit Agreement as
of the date first above written. Each of the undersigned further agrees that the
obligations of each of the undersigned pursuant to the Guaranty of Payment, the
Security Agreement and any other Loan Document to which any of the undersigned
is a party shall remain in full force and effect and be unaffected hereby.

                        ONCO Investment Company
                        Oglebay Norton Management Company
                        Oglebay Norton Industrial Sands, Inc.
                        Oglebay Norton Terminals, Inc.
                        Oglebay Norton Engineered Materials, Inc.
                        Michigan Limestone Operations, Inc.
                        Global Stone Corporation (successor by merger to
                                 Oglebay Norton Acquisition Company)
                        Global Stone Tenn Lutrell Company
                        Global Stone Chemstone Corporation
                        Global Stone St. Clair, Inc.
                        Global Stone Management Company
                        Global Stone Filler Products Company
                        Global Stone James River, Inc.
                        GS PC, Inc.
                        Oglebay Norton Minerals, Inc.
                        Oglebay Norton Specialty Minerals, Inc.
                        ON Coast Petroleum Company
                        ON Marine Services Company
                        ONCO WVA, Inc.
                        ONTEX, Inc.
                        Saginaw Mining Company
                        Erie Navigation Company
                        Erie Sand and Gravel Company
                        Erie Sand Steamship Co.
                        Mountfort Terminal, Ltd.
                        Serve-All Concrete, Inc.
                        S & J Trucking, Inc.

                        By:
                           -------------------------------------------
                               Rochelle F. Walk, as Vice President and
                               Secretary of each of the companies listed above.

                        Texas Mining, LP, by its General Partner
                        ONTEX, Inc.

                               By:
                                  ------------------------------------
                                       Rochelle F. Walk
                                       Vice President and Secretary

                        Global Stone PenRoc, LP, by its General Partner,
                        GS PC, Inc,.

                               By:
                                  ------------------------------------
                                       Rochelle F. Walk
                                       Vice President and Secretary

                                       S-4
                       Amendment No.6 to Credit Agreement

<PAGE>

                        Oglebay Norton Marine Services Company, L.L.C., by its
                        Member ON Marine Services Company

                               By:
                                  ------------------------------------
                                       Rochelle F. Walk
                                       Vice President and Secretary

                        Oglebay Norton Marine Management Company, LLC.
                        by its member  Oglebay  Norton Marine Services Company,
                        L.L.C.

                               By:
                                  ------------------------------------
                                       Rochelle F. Walk
                                       Vice President and Secretary

                        Global Stone Portage, LLC by its member

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

                               By:
                                  ------------------------------------
                                       Rochelle F. Walk
                                       Vice President and Secretary

                                       S-5
                       Amendment No. 6 to Credit Agreement

<PAGE>

                                   Schedule 3
                       Amendment No. 6 to Credit Agreement