147 stamps here...
Joachim Esche has made a complete (large !, 1420 stamps) list on minerals on stamps. You can download it here...
Jim Groves sent some first-day-prints of his geology/mineralogy stamp collection !
Click below on the thumbails to see the first-day-prints in detail...
Below are all single series/stamps:

Angola, 1970
Australia, 1973
Austria, 1986
Brasil, 1977
Brasil, 1989

Cyprus, 1983
Finland, 1986
France, 1989-1990
France, 1986
Germany, 1972
Also see: keimarstamps on german stamps.
Germany, 1969
Germany, 1974
Germany, 1978
Greece, 1980
Hungary, 1969
Israel, 1981
Israel, 1968
Kenya, 1977
Kenya, 1977
Korea, 1986
Liechtenstein, 1989
Madagascar, 1989
Maroc, 1975
Maroc, 1987
Mocambique, 1979
Monaco, 1990
New Zealand, 1982
Poland, 1979
Portugal, 1971
Rhodesia, 1966
Russia, 1963
South Africa, 1980
Sri Lanka, 1976
Switzerland, 1958
Switzerland, 1959
Switzerland, 1960
Switzerland, 1961
Thailand, 1990
Turkey, 1979
Tristan da Cunha, 1987
Uganda, 1988
USA, 1974
Zaire, 1983
Zimbabwe (Rhodesia), 1978
Zimbabwe, 1978
Zimbabwe, 19??
Other sites:
rockhounds.com, albany stamps, xlizd.com, rik dillen, stampmin, marina,