<PAGE>

                                                                    Exhibit 10.1

                                                                  EXECUTION COPY

                                WAIVER LETTER AND
                                 AMENDMENT NO. 7
                                       TO
                                CREDIT AGREEMENT

     This WAIVER LETTER AND AMENDMENT NO. 7 TO CREDIT AGREEMENT (this "Agreement
and Amendment"), made as of June 13, 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,
Amendment No. 5 to Credit Agreement, dated as of January 8, 2003, and Waiver
Letter and Amendment No. 6 to Credit Agreement, dated as of March 31, 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
(the "Financial Covenant Violations") for periods of determination occurring
prior to the Waiver Expiration Date (as defined below);

     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:

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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 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 5.7B of the Credit Agreement) 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) a new definition "Amendment No. 7 Closing Date," shall be added to Article I
and inserted therein in appropriate alphabetical order, to read as set forth
below, (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 and (z) the definition of "Waiver Expiration Date" shall be amended
to read as set forth below:

     "Amendment No. 7 Closing Date" shall mean the date on which the "Effective
Date" (as such term is defined in Section 5 of that certain Waiver Letter and
Amendment No. 7 to Credit Agreement, dated as of June 13, 2003) occurs.

     "Applicable Margin" shall mean:

          (a) for the period commencing on the Amendment No. 7 Closing Date
     until and including the Waiver Expiration Date, (i) four hundred fifty
     (450) basis points for each LIBOR Interest Segment, and (ii) two hundred
     twenty-five (225) basis points for Prime Rate Loans, and . . .

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

     "Waiver Expiration Date" means the earlier of: (i) August 15, 2003 or (ii)
July 31, 2003 (if the Borrower is unable by July 9, 2003 to obtain a waiver of
any Events of Default under the 2002 Senior Secured Fund Notes which waiver
extends until August 15, 2003 or later).


                       Amendment No. 7 to Credit Agreement

                                       2


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     3.2 Amendment to Section 5.3. Section 5.3 of the Credit Agreement is hereby
amended as follows: (w) with respect to the fiscal quarter ending June 30, 2003
only, paragraph (a) of Section 5.3 shall be amended so that the financial
statements with respect to such fiscal quarter shall be required to be released
to the public and delivered to each Bank on August 1, 2003 and such financial
statements with respect to such fiscal quarter (with any adjustments made to
such financial statements) shall be disclosed in the Borrower's 10Q and
delivered to each Bank by August 15, 2003, (x) with respect to the fiscal
quarter ending June 30, 2003 only, paragraph (c) of Section 5.3 shall be amended
so that the Borrower shall be required to deliver to each Bank on August 1, 2003
calculations of the financial covenants set forth in Section 5.7B (rather than
Section 5.7) of the Credit Agreement which calculations shall be based on the
financial statements delivered to the Banks on August 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 June 30, 2003), (y) with
respect to the fiscal quarter ending June 30, 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 August 15, 2003 a Compliance Certificate and
calculations of the financial covenants set forth in Section 5.7B (rather than
Section 5.7) of the Credit Agreement which calculations shall be based on the
financial statements delivered to the Banks on August 15, 2003 and certified by
a Financial Officer of the Borrower.

     3.3 Temporary Financial Covenants. In the event the Effective Date occurs,
then on and after June 16, 2003 until and including the Waiver Expiration Date,
Section 5 of the Credit Agreement shall be amended to add Section 5.7B 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 the Waiver
Expiration Date):

     SECTION 5.7B TEMPORARY FINANCIAL COVENANTS

          (a) LEVERAGE RATIO. The Companies shall not suffer or permit at any
     time the Leverage Ratio to exceed 8.75 to 1.00 on June 16, 2003 through and
     including the Waiver Expiration Date.

          (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 5.25 to 1.00
     on June 16, 2003 through and including the Waiver Expiration Date, 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 1.15 to 1.00 on June 16, 2003 through
     and including the Waiver Expiration Date, 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 Fixed Charges (excluding from Pro-Forma Fixed
     Charges for purposes of


                       Amendment No. 7 to Credit Agreement

                                       3

<PAGE>

     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 0.60 to 1.00 on June 16, 2003 through and including the
     Waiver Expiration Date, 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 June 30, 2003, an amount equal to $87,678,000; 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
     $51,500,000 on June 16, 2003 through and including the Waiver Expiration
     Date, 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 June 16, 2003 through and including the Waiver Expiration Date.

     3.4 Addition to Section 5.24. Section 5.24 of Article V is amended by
adding the following sentence at the end of such Section:

     In the event that Borrower agrees to any increase in existing interest rate
     or fees, or the creation or increase of penalty or premium, or the granting
     of any other right or chose having economic value with respect to any
     contract or agreement for the borrowing of money in excess of Two Million
     Dollars ($2,000,000) and, notwithstanding the amount thereof, the 2002
     Senior Secured Fund Notes, the Indenture, and any loans or capital leases
     for the purchase or lease of assets extended by US Bank National
     Association, National City Bank and their affiliates, then: (i) with
     respect to any such increase in existing interest or fees, the Banks shall
     receive the same increase in any existing interest rate and fees or (ii)
     with respect to any such creation, increase or grant of a penalty or
     premium or any other right or chose having economic value, the Banks shall
     receive an amount equal to (x) the Debt owed to the Banks hereunder
     multiplied by (y) a percentage equal to (A) the aggregate amount or value
     of such penalty, premium, right or chose divided by (B) the aggregate
     outstanding amount of such contract or agreement for borrowed money.

     3.5 Addition of Section 5.33. Article V is amended by adding Section 5.33
thereto to read as follows:

                       Amendment No. 7 to Credit Agreement

                                        4

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          SECTION 5.33. APPRAISALS. Borrower shall: (i) use its best efforts to
     furnish to Agent no later than July 15, 2003 final versions of each Haas
     appraisal of each of the Companies' material mineral and mining operations
     (other than with respect to Special Minerals Velarde and Kings Mountain
     operations, in form and substance acceptable to Agent and (ii) use its best
     efforts to furnish to Agent no later than July 31, 2003 final versions of
     the Haas appraisal of Special Minerals Velarde and Kings Mountain
     operations, in form and substance acceptable to Agent.

     3.6 Addition of Section 5.34. Article V is amended by adding Section 5.34
thereto to read as follows:

          SECTION 5.34. FINAL OFFERING MEMORANDA. Borrower shall furnish to
     Agent true and complete copies of each final offering memorandum generated
     with respect to any proposed sale of any of the Companies' assets as soon
     as they are completed by Borrower's investment banker Harris Williams.
     Borrower shall also furnish to Agent: (i) relevant industry information and
     resumes by no later than July 9, 2003 and (ii) relevant valuation reports
     and estimated time schedules for closing such contemplated sales of assets
     of the Companies by no later than July 15, 2003.

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

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 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

                       Amendment No. 7 to Credit Agreement

                                        5

<PAGE>

representations and warranties of Borrower set forth in the Credit Agreement are
true and correct in all material respects 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 as, 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. 7 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. 7 to Loan Agreement. Agent shall have
received from Borrower and Banks constituting Majority Banks an original
counterpart of the Waiver Letter and Amendment No. 7 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.

     5.3 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 Agreement and Amendment Fee; Legal Expenses to Date. Agent shall have
received, for the benefit of each Bank (including Agent in its capacity as a
Bank) approving and executing this Agreement and Amendment, a one time fee in
the amount of ten (10) basis points multiplied by the Revolving Credit
Commitment of such Bank. In addition, the Agent shall have received payment of
all currently outstanding expenses of Agent incurred in connection with

                       Amendment No. 7 to Credit Agreement

                                        6

<PAGE>

outstanding fees and expenses of counsel to Agent in connection with the matters
contemplated hereby or undertaken to date in connection with the Credit
Agreement and Loan Agreement.

     5.5 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.

     5.6 Other Deliveries. Agent shall have received from Borrower any other
agreements previously discussed as being required in connection with this
Amendment , in form and substance acceptable to Agent, executed and delivered by
a duly authorized officer of Borrower.

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]

                       Amendment No. 7 to Credit Agreement

                                        7

<PAGE>

     IN WITNESS WHEREOF, Borrower has caused this Waiver Letter and Amendment
No. 7 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                       Name: Julie A. Boland
          Cleveland, Ohio 44114-1151            --------------------------------
          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 Bank
          Detroit, Michigan 48226          One, Michigan)
          Attention: Large Corporate       By:__________________________________
          Banking Division                 Name:________________________________
                                           Title:_______________________________


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

                       Amendment No. 7 to Credit Agreement

                                       S-1

<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:  ___________________               GOLDMAN SACHS CREDIT
                                            PARTNERS LP II
          ___________________
          ___________________               By:_________________________________
          ___________________               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:______________________________

                       Amendment No. 7 to Credit Agreement

                                       S-2

<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       Name:_______________________________
          Banking Division                 Title:______________________________


Address:  _______________________          ______________________________
          _______________________
          _______________________          By:_________________________________
          _______________________          Name:_______________________________
                                           Title:______________________________


Address:  _______________________          ______________________________
          _______________________
          _______________________          By:_________________________________
          _______________________          Name:_______________________________
                                           Title:______________________________

                       Amendment No. 7 to Credit Agreement

                                       S-3

<PAGE>

Address:  _______________________          ______________________________
          _______________________
          _______________________          By:__________________________________
          _______________________          Name:________________________________
                                           Title:_______________________________

                       Amendment No. 7 to Credit Agreement

                                       S-4

<PAGE>

                          ACKNOWLEDGMENT OF GUARANTORS

     Each of the undersigned consents and agrees to and acknowledges the terms
of the foregoing Waiver Letter and Amendment No. 7 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

                       Amendment No. 7 to Credit Agreement

                                       S-5

<PAGE>

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

                                        By:____________________________________
                                             Rochelle F. Walk,
                                             Vice President and Secretary

                                    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

                       Amendment No. 7 to Credit Agreement

                                       S-6