RECITALS: ---------

   1
                                                                     Exhibit 4.8
                                                                     -----------

                             SUPPLEMENTAL INDENTURE
                             ----------------------


         Reference is made to that certain Indenture, dated as of February 1,
1999, by and among Oglebay Norton Company, a Delaware corporation ("Original
ONC"), the guarantors party thereto and NORWEST BANK MINNESOTA, NATIONAL
ASSOCIATION, as Trustee (the "Indenture"). Capitalized terms used without
definition herein have the meanings given to them in the Indenture.

                                    RECITALS:
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         A. Pursuant to an Agreement and Plan of Merger, dated as of March 3,
1999, by and among Original ONC, Oglebay Norton Holding Company, a Delaware
corporation ("Holding Company"), ONCO Investment Company, a Delaware
corporation, and Oglebay Norton Merger Company, a Delaware corporation ("Merger
Company"), Merger Company will merge (the "Merger") with and into Original ONC,
with Original ONC as the surviving corporation;

         B. Immediately after the Merger, Original ONC will become an indirect
subsidiary of Holding Company and change its name to "ON Marine Services
Company," and Holding Company will change its name to Oglebay Norton Company
("New ONC");

         C. The Indenture permits the Merger only if New ONC enters into this
Supplemental Indenture and assumes all of the obligations of Original ONC as the
"Company" thereunder;

         NOW, THEREFORE, in consideration of the above premises, New ONC agrees,
for the benefit of the Holders, as follows:

         Effective with the Merger, New ONC hereby expressly and fully and
unconditionally assumes each and every obligation, covenant, agreement and
undertaking of Original ONC under the Financing Documents as if New ONC has been
originally party thereto as the "Company." Upon effectiveness of such assumption
and the execution and delivery to the Trustee by Original ONC of a Supplemental
Indenture to become a Guarantor under the Financing Documents, Original ONC
shall cease to be the "Company" under the Financing Documents.

         The laws of the State of New York shall govern this Supplemental
Indenture without giving effect to any conflicts of law principles thereof.




   2


         IN WITNESS WHEREOF, the undersigned has caused this Assumption
Agreement to be duly executed, all as of March 5, 1999.

                                       OGLEBAY NORTON HOLDING COMPANY,
                                       a Delaware corporation, to be renamed
                                       OGLEBAY NORTON COMPANY

                                       By: /s/ Xxxx X. Xxxxx
                                           -------------------------------------
                                             Name: Xxxx X. Xxxxx
                                             Title: President and CEO

                                       NORWEST BANK MINNESOTA,
                                       NATIONAL ASSOCIATION

                                       By: /s/ Xxxxxx X. Xxxxxxxxx
                                           -------------------------------------
                                             Name: Xxxxxx X. Xxxxxxxxx
                                             Title: Assistant Vice President