Gypsum, Calcite, Sphalerite
Joplin Field, Tri-State District, Jasper Co., Missouri, USA
Cabinet, 15.3 x 10.8 x 3.4 cm
An old Tri-State specimen that is quite unusual: on a surface of deep red micro-sphalerites (a few of them larger, with one isolated crystal measuring 1 cm) are several snowy white crystals. These are very sharp crystals of calcite that have been wrapped in a snowy layer of gypsum - and the note from George Feist on the bottom of its base indicates he thought that pseudomorphism was going on. If you look closely, you can see the sharp faces of the calcite crystals where they show in places through the gypsum, so this may be a replacement caught in progress or simply a very thick (and unusual) coating. Ex. George Feist Collection.