EXHIBIT 3.13

                                State of Delaware
                        Office of the Secretary of state
    
     I, EDWARD J. FREEL, SECRETARY OF STATE OF THE STATE OF DELAWARE, DO HEREBY
CERTIFY THAT "MINERAL RESOURCE TECHNOLOGIES, L.L.C." IS DULY FORMED UNDER THE
LAWS OF THE STATE OF DELAWARE AND IS IN GOOD STANDING AND HAS A LEGAL EXISTENCE
NOT HAVING BEEN CANCELLED OR REVOKED SO FAR AS THE RECORDS OF THIS OFFICE SHOW
AND IS DULY AUTHORIZED TO TRANSACT BUSINESS.

     THE FOLLOWING DOCUMENTS HAVE BEEN FILED: CERTIFICATE OF LIMITED LIABILITY
COMPANY, FILED THE TWENTY-FIRST DAY OF NOVEMBER, A.D. 1995, AT 9 O'CLOCK A.M.

     AND I DO HEREBY FURTHER CERTIFY THAT THE AFORESAID CERTIFICATES ARE THE
ONLY CERTIFICATES ON RECORD OF THE AFORESAID LIMITED LIABILITY COMPANY.

     AND I DO HEREBY FURTHER CERTIFY THAT THE ANNUAL TAXES HAVE BEEN PAID TO
DATE.


/S/ Edward J. Freel
- --------------------
Edward J. Freel, Secretary of State




                                State of Delaware
                        Office of the Secretary of state

     I, EDWARD J. FREEL, SECRETARY OF STATE OF THE STATE OF DELAWARE, DO HEREBY
CERTIFY THE ATTACHED IS A TRUE AND CORRECT COPY OF THE CERTIFICATE OF LIMITED
LIABILITY COMPANY OF "MINERAL RESOURCE TECHNOLOGIES, L.L.C.," FILED IN THIS
OFFICE ON THE TWENTY-FIRST DAY OF NOVEMBER, A.D. 1995, AT 9 O'CLOCK A.M.


/S/ Edward J. Freel
- --------------------
Edward J. Freel, Secretary of State




                            CERTIFICATE OF FORMATION
                                       OF
                      MINERAL RESOURCE TECHNOLOGIES, L.L.C.

     This Certificate of Formation of Mineral Resource Technologies, L.L.C. (the
"L.L.C.") is being duly executed and filed by MRT Management Corp., an
authorized person, to form a limited liability company under the Delaware
Limited Liability Company Act.

     FIRST: The name of the limited liability company formed hereby is Mineral
Resource Technologies, L.L.C.

     SECOND: The address of the registered office of the L.L.C. in the State of
Delaware is 32 Lockerman Square, Suite L-100, Dover, Delaware 19904. The
L.L.C.'s registered agent for service of process at that address is The
Prentice-Hall Corporation System, Inc.

     IN WITNESS WHEREOF, the undersigned has caused this Certificate of
Formation to be duly executed as of November 21, 1995.


MRT MANAGEMENT CORP.


By:  /s/ Nathan Bistricer
     ---------------------
Vice President