Presented below are links to some other web sites which feature gem, rock, and mineral postage stamps.
Hans Marquardt
Mineralogie - Paläontologie - Geologie
und
Bergabaumotive auf Briefmarken
Mineral stamps (updated 2009)
Stéphane Gigandet
A collection of stamps figuring photos or images of minerals, cristals, gems, rocks, fossils and meteorites from around the world.
Philathelic Mineralgy (updated 2010)
Richard Busch
Gem, Rock, and Mineral Postage Stamps
From Around the World