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                                                                      Exhibit 10

                            FIFTH AMENDMENT AGREEMENT


         THIS FIFTH AMENDMENT AGREEMENT ("Amendment") is made as of the 23rd day
of July, 1999, by and among OGLEBAY NORTON COMPANY, formerly known as Oglebay
Norton Holding Company, a Delaware corporation ("Borrower"), as assignee of ON
Marine Services Company, formerly known as Oglebay Norton Company ("Original
Borrower"), the banking institutions listed on Schedule 1 to the Credit
Agreement, as hereinafter defined ("Banks"), and KEYBANK NATIONAL ASSOCIATION,
as agent for the Banks ("Agent"):

         WHEREAS, Original Borrower, Agent and the Banks entered into a certain
Credit Agreement dated as of May 15, 1998, and assumed by Borrower as of March
5, 1999, as amended, and as it may from time to time be further amended,
restated or otherwise modified, which provides, among other things, for loans,
letters of credit, and other financial accommodations aggregating Two Hundred
Thirty-Two Million Dollars ($232,000,000), all upon certain terms and conditions
stated therein ("Credit Agreement");

         WHEREAS, Borrower, Agent and the Banks desire to amend the Credit
Agreement to modify certain provisions thereof; and

         WHEREAS, each term used herein shall be defined in accordance with the
Credit Agreement.

         NOW, THEREFORE, in consideration of the premises and mutual covenants
herein contained and for other valuable considerations, Borrower, Agent and the
Banks hereby agree as follows:

         1. Article I of the Credit Agreement is hereby amended to delete the
definition of "Leverage Ratio" in its entirety and to insert in place thereof
the following:

                  "Leverage Ratio" shall mean, at any time, the ratio for the
         Companies of (a) Total Funded Indebtedness (based upon the financial
         statements of the Companies for the most recently completed fiscal
         quarter) to (b) Consolidated Pro-Forma EBITDA (based upon the financial
         statements of the Companies for the most recently completed four (4)
         fiscal quarters).

         2. The Credit Agreement is hereby amended to delete subpart (b) from
Section 5.7 in its entirety and to insert in place thereof the following:

                  (b) LEVERAGE RATIO. The Companies shall not suffer or permit
         at any time the Leverage Ratio to exceed (i) 5.00 to 1.00 on June 30,
         1998 through December 31, 1999, (ii) 4.75 to 1.00 from January 1, 2000
         through December 30, 2000, and (iii) 4.50 to 1.00 on December 31, 2000
         and thereafter, based upon the financial statements of the Companies
         for the most recently completed four (4) fiscal quarters.

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         3. The Credit Agreement is hereby amended to delete subpart (d) from
Section 5.7 in its entirety and to insert in place thereof the following:
                  (d) INTEREST COVERAGE. The Companies shall not suffer or
         permit at any time the ratio of (i) Consolidated Pro-Forma Pre-Tax
         Earnings plus Consolidated Pro-Forma Interest Expense to (ii)
         Consolidated Pro-Forma Interest Expense to be less than 1.50 to 1.00,
         based upon the financial statements of the Companies for the most
         recently completed four (4) fiscal quarters.

         4. The Credit Agreement is hereby amended to delete subpart (g) from
Section 5.7 in its entirety and to insert in place thereof the following:

                  (g) CONSOLIDATED PRO-FORMA EBITDA. The Companies shall not
         suffer or permit at any time Consolidated Pro-Forma EBITDA to be less
         than (i) Sixty-Six Million Dollars ($66,000,000) on June 30, 1998
         through June 30, 2000, and (ii) Seventy Million Dollars ($70,000,000)
         on July 1, 2000 and thereafter, based upon the financial statements of
         the Companies for the most recently completed four (4) fiscal quarters.

         5. Borrower has informed Agent and the Banks that Global Stone
Corporation intends to sell all of the outstanding capital stock of Global Stone
Ingersoll Ltd ("Ingersoll Stock"). Borrower has requested that Agent and the
Banks consent to the sale of the Ingersoll Stock and that Agent and the Banks
waive any violation of Section 5.12 as a result of such sale. Agent and the
Banks hereby consent to the sale of the Ingersoll Stock and grant such waiver on
the condition that after giving effect to this Amendment, no Unmatured Event of
Default or Event of Default exists, or immediately thereafter would exist, under
the Credit Agreement. This Amendment shall serve as evidence of such consent and
waiver.

         6. Concurrently with the execution of this Amendment, Borrower shall:

         (a) cause each Pledgor to consent and agree to and acknowledge the
terms of this Amendment;

         (b) pay an amendment fee to each Bank that executes this Amendment
prior to 12:01 P.M. (Cleveland, Ohio time) on July 23, 1999 (each such Bank, an
"Executing Bank") in an amount equal to (i) twelve and one-half (12 1/2) basis
points, times (ii) the Total Commitment Amount, times (iii) the Commitment
Percentages of such Executing Bank. Such amendment fee shall be paid to Agent
for the pro rata benefit of the Executing Banks; and

         (c) pay all legal fees and expenses of Agent in connection with this
Amendment.

         7. Borrower hereby represents and warrants to Agent and the Banks that
(a) Borrower has the legal power and authority to execute and deliver this
Amendment; (b) the officers executing this Amendment have been duly authorized
to execute and deliver the same and bind Borrower with respect to the provisions
hereof; (c) the execution and delivery hereof by Borrower and the performance
and observance by Borrower of the provisions hereof do not

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violate or conflict with the organizational agreements of Borrower or any law
applicable to Borrower or result in a breach of any provision of or constitute a
default under any other agreement, instrument or document binding upon or
enforceable against Borrower; (d) no Unmatured Event of Default or Event of
Default exists under the Credit Agreement, nor will any occur immediately after
the execution and delivery of this Amendment or by the performance or observance
of any provision hereof; (e) neither Borrower nor any Pledgor is aware of any
claim or offset against, or defense or counterclaim to, any of Borrower's or any
Pledgor's obligations or liabilities under the Credit Agreement or any Related
Writing; and (f) this Amendment constitutes a valid and binding obligation of
Borrower in every respect, enforceable in accordance with its terms.

         8. Each reference that is made in the Credit Agreement or any other
writing to the Credit Agreement shall hereafter be construed as a reference to
the Credit Agreement as amended hereby. Except as herein otherwise specifically
provided, all provisions of the Credit Agreement shall remain in full force and
effect and be unaffected hereby. This Amendment is a Related Writing as defined
in the Credit Agreement.

         9. Borrower and each Pledgor, by signing below, hereby waives and
releases Agent and each of the Banks and their respective directors, officers,
employees, attorneys, affiliates and subsidiaries from any and all such claims,
offsets, defenses and counterclaims of which Borrower and any Pledgor is aware,
such waiver and release being with full knowledge and understanding of the
circumstances and effect thereof and after having consulted legal counsel with
respect thereto.

         10. This Amendment may be executed in any number of counterparts, by
different parties hereto in separate counterparts and by facsimile signature,
each of which when so executed and delivered shall be deemed to be an original
and all of which taken together shall constitute but one and the same agreement.

         11. The rights and obligations of all parties hereto shall be governed
by the laws of the State of Ohio, without regard to principles of conflicts of
laws.

                  [Remainder of Page Intentionally Left Blank]

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         12. JURY TRIAL WAIVER. BORROWER, PLEDGORS, AGENT AND EACH OF THE BANKS
WAIVE ANY RIGHT TO HAVE A JURY PARTICIPATE IN RESOLVING ANY DISPUTE, WHETHER
SOUNDING IN CONTRACT, TORT OR OTHERWISE, AMONG BORROWER, AGENT AND THE BANKS, OR
ANY THEREOF, ARISING OUT OF, IN CONNECTION WITH, RELATED TO, OR INCIDENTAL TO
THE RELATIONSHIP ESTABLISHED AMONG THEM IN CONNECTION WITH THIS AGREEMENT OR ANY
NOTE OR OTHER INSTRUMENT, DOCUMENT OR AGREEMENT EXECUTED OR DELIVERED IN
CONNECTION HEREWITH OR THE TRANSACTIONS RELATED THERETO.

                                        OGLEBAY NORTON COMPANY,
                                        formerly known as Oglebay Norton
                                        Holding Company


                                        Michael F. Biehl, Treasurer


                                        KEYBANK NATIONAL ASSOCIATION,
                                        as Agent and as a Bank


                                        Lawrence A. Mack, Senior Vice
                                        President


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                                  BANK ONE, NA




                                  THE BANK OF NOVA SCOTIA




                                  COMERICA BANK




                                  THE HUNTINGTON NATIONAL BANK




                                  MELLON BANK, N.A.



                                  BANK OF AMERICA NATIONAL TRUST
                                  AND SAVINGS ASSOCIATION




                                  HARRIS TRUST AND SAVINGS BANK




                                  THE CHASE MANHATTAN BANK

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                                  FIRSTAR BANK, NATIONAL
                                  ASSOCIATION, successor by merger
                                  to Star Bank National Association




                                  FLEET BANK, N.A.




                                  ABN AMRO BANK N.V.,
                                  PITTSBURGH BRANCH




                                  FIFTH THIRD BANK OF NORTHEASTERN
                                  OHIO

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                            GUARANTOR ACKNOWLEDGMENT
                            ------------------------

         Each of the undersigned consents and agrees to and acknowledges the
terms of the foregoing Fifth Amendment Agreement. Each of the undersigned
further agrees that the obligations of each of the undersigned pursuant to the
Guaranty of Payment and the other Loan Documents executed by each of the
undersigned shall remain in full force and effect and be unaffected hereby.

                              ONCO     Investment Company (a Delaware
                                       corporation, in its own capacity
                                       and as successor by merger to
                                       Oglebay Norton Holding Company,
                                       an Ohio corporation, and ONCO
                                       Investment Company, an Ohio
                                       corporation)
                              ON Marine Services Company (formerly known as
                                       Oglebay Norton Company)
                              Oglebay Norton Industrial Minerals, Inc.
                              Oglebay Norton Management Company
                              Oglebay Norton Industrial Sands, Inc.
                              Colorado Silica Sand, Inc.
                              Oglebay Norton Terminals, Inc.
                              Oglebay Norton Engineered Materials, Inc.
                              Global Stone Corporation (successor by merger to
                              Oglebay Norton Acquisition Company)
                              Global Stone Port Inland, Inc.
                              Moreland Development Company
                              Western Wisconsin Materials, Inc.
                              Global Stone (USA) Inc.
                              Global Stone Tenn Lutrell Company
                              Global Stone Chemstone Corporation
                              Global Stone Detroit Lime Company
                              Global Stone St. Clair, Inc.
                              Global Stone PenRoc Inc.
                              Global Stone Filler Products Company


                                   Michael F. Biehl as Treasurer of
                                   each of the companies listed above






                              Texas Mining, LP

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                                      By: Oglebay Norton Industrial Sands, Inc.,
                                                  General Partner


                                            Michael F. Biehl, Treasurer

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