Exhibit 4.1 SUPPLEMENTAL INDENTURE Reference is made to that certain Indenture, dated as of February 1, 1999, by and among Oglebay Norton Company (formerly known as Oglebay Norton Holding Company), a Delaware corporation ("Oglebay"), the guarantors...

                                                                     Exhibit 4.1

                            SUPPLEMENTAL INDENTURE

     Reference is made to that certain Indenture, dated as of February 1, 1999,
by and among Oglebay Norton Company (formerly known as Oglebay Norton Holding
Company), a Delaware corporation ("Oglebay"), 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:

     A.  Section 4.13 of the Indenture provides, inter alia., that "[i]f (a) the
Company or any Restricted Subsidiary shall organize, acquire or otherwise invest
in another Person that becomes a Restricted Subsidiary, or (b) any Restricted
Subsidiary that is not already a Guarantor shall become an obligor under the
Senior Credit Facility, then the Company shall cause such Restricted Subsidiary
to (i) execute and deliver to the Trustee a supplemental Indenture pursuant to
which such Restricted Subsidiary shall become a Guarantor..."

     X.  Xxxxxxx Xxxxxx Management Company, an Ohio corporation, has become an
obligor under the Senior Credit Facility and a Restricted Subsidiary has
organized Global Stone PenRoc, LP, a Pennsylvania limited partnership, and
Oglebay Norton Management Company and Global Stone PenRoc, LP are Restricted
Subsidiaries and are therefore required to become Guarantors under the Indenture
unless they are designated as Unrestricted Subsidiaries;

     NOW, THEREFORE, in consideration of the above premises, Oglebay Norton
Management Company and Global Stone PenRoc, LP agree, for the benefit of the
Holders, as follows:

     Effective with the date hereof, Oglebay Norton Management Company and
Global Stone PenRoc, LP each hereby expressly and fully and unconditionally
agrees to become a Guarantor 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.

     IN WITNESS WHEREOF, the undersigned has caused this Supplemental Indenture
to be duly executed, as of April 3, 2000.

     OGLEBAY NORTON MANAGEMENT                   NORWEST BANK MINNESOTA,
          COMPANY                                NATIONAL ASSOCIATION

     By: /s/ Xxxxxxx X. Xxxxx                   By:
        ---------------------                       --------------------
          Xxxxxxx X. Xxxxx                      Title:
          Treasurer                                   ------------------

     GLOBAL STONE PENROC, LP
     By: GS PC, Inc., its general partner

     By: /s/ Xxxxxxx X. Xxxxx
         --------------------
          Xxxxxxx X. Xxxxx
          Treasurer