Exhibit 10.18 June 20, 1996 Mr. Gene G. Elam Vice President, Finance and Chief Financial Officer 650 California Street, 9th Floor San Francisco, California 94108-2788 Dear Gene: In response to your letter of June 10, 1996, I have included a revised...

                                                              Exhibit 10.18


                                                     June 20, 1996


Xx. Xxxx X. Xxxx
Vice President, Finance
  and Chief Financial Officer
000 Xxxxxxxxxx Xxxxxx, 0xx Xxxxx
Xxx Xxxxxxxxx, Xxxxxxxxxx 00000-2788

Dear Xxxx:

In response to your letter of June 10,  1996, I have  included a revised  letter
agreement to Amendment 1 to the Joint  Operating  Agreement  inserting the words
"per annum" after the amount $11,290,000.  Once this is executed, please forward
an original to Xxxxx Xxxxx of our office and retain the  duplicate  original for
your files.

With  regard  to your  understanding  of how the  letter,  in  conjunction  with
Amendment  1,  will  operate,  we agree  with  your  summary  as  detailed.  For
clarification  purposes,  escalation  of the  Corporate  G&A Charge for calendar
years  1997,  1998,  and  the  first  half of 1999  will  be made  based  on the
percentage  change  in the  annual  GNP  Deflator  Index  for  1995 and 1996 for
calendar year 1997, the  percentage  change in the annual GNP Deflator Index for
1996 and 1997 for calendar year 1998,  and the  percentage  change in the annual
GNP Deflator Index for 1997 and 1998 for calendar year 1999.

We appreciate your assistance in finalizing this matter.

                                                     Very truly yours,






NDP/dpr
Enclosures
cc:      Xxx Xxxxxxxxx
         Xxxxxx Xxxxxx (w/o enc.) 
         Xxxxx Xxxxx (w/o enc.)




                                                     June 17, 1996


IMC Global Operations Inc.
0000 Xxxxxxx Xxxx
Xxxxxxxxxx, Xxxxxxxx 00000


Homestake Mining Company
000 Xxxxxxxxxx Xxxxxx, 00xx Xxxxx
Xxx Xxxxxxxxx, XX 00000

Re:      Corporate G&A Charge

Gentlemen:

Reference is made to Amendment No. 1 to Joint Operating Agreement  ("Amendment")
dated as of July 1,  1993  among  Freeport-McMoran  Resource  Partners,  Limited
Partnership,  IMC Global Operations Inc.  (formerly,  IMC Fertilizer,  Inc.) and
Homestake  Sulphur  Company.  Pursuant to paragraph 5(B) of the  Amendment,  the
parties agree that the Corporate G&A Charge for the Adjustment  Period from July
1, 1996 to June 30, 1999 shall be $11,290,000  per annum,  subject to escalation
in the manner provided for in paragraph 1.1 of the Amendment.

                                      Yours truly,


                                      FREEPORT-McMoRan RESOURCE
                                      PARTNERS, LIMITED PARTNERSHIP

                                      By:__________________
                                      Title:  Vice President - General Counsel



AGREED:

IMC GLOBAL OPERATIONS INC.

By:____________________
Title:__________________


HOMESTAKE SULPHUR COMPANY

By:____________________
Title:__________________