Serpentine: Serpentine may refer to a single mineral but more often to a group of minerals including antigorite,... (read full)

Schorl Tourmaline: Schorl is the black, opaque, sodium iron rich variety of Tourmaline, a complex borosilicate with a ... (read full)

Scheelite: Scheelite is a mineral in the group of Sulfates, Chromates, Molybdates, Tungstates. It has the same ... (read full)

Scapolite: Scapolite is a mixed crystal series, a complicated sodium calcium aluminum silicate group composed o... (read full)

Sardonyx: Sardonyx is a gem variety of reddish-brown colored sard with white or black banded chalcedony or ony... (read full)

Sard: Sard is the uniformly colored red-brown or brownish-yellow variety of Chalcedony, which in turn is a... (read full)

Sapphire: Sapphire is the blue variety of Corundum. Sapphires can be a very dark blue, to the point of seemin... (read full)

Rutile: Rutile with anatase and brookite is a trimorph of titanium oxide in the Rutile group. It forms char... (read full)

Ruby: Ruby is the most valuable variety of Corundum. The color varies from fiery vermilion to violet red,... (read full)

Rubellite Tourmaline: Rubellite is the pink to red variety of Tourmaline, which is a complex borosilicate of aluminum and ... (read full)