SMITHSONITE
Smithsonite is a distinctive zinc carbonate mineral
(ZnCO3). It typically forms finely-crystalline botryoidal
layers and coatings. It's characterized by having a nonmetallic,
subvitreous luster, just about any color, a hardness of 4 to 4.5, a white
streak, rhombohedral cleavage (this can only be seen if nice, decent-sized
crystals are present), and is moderately heavy for its size. It bubbles
slightly in acid.
Smithsonite forms in supergene environments from the
breakdown of sphalerite. It also occurs in some hydrothermal veins.
Smithsonite (field of view 2.9 cm across) from the Kelly Mine, western margin of
the northern Magdalena Mountains, southeast of Magdalena, western Socorro
County, west-central New Mexico, USA.