A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 5600 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

The arsenide minerals contain one or more arsenide anions (As-3). The arsenides are usually considered together with the sulfide minerals, the sulfarsenide minerals, and the telluride minerals.

Skutterudite is an uncommon cobalt-nickel arsenide mineral ((Co,Ni)As3). Skutterudite has a metallic luster, bright silvery color, black streak, no cleavage, moderate hardness (H = 5.5 to 6), and moderately high density. It can be an important ore mineral of cobalt and nickel, and is typically found in hydrothermal veins.

The beautifully crystalline skutterudite seen here is from a cobalt-nickel mineralized vein in a fault system within the Bou Azzer-El Graara Ophiolite of Morocco. The ophiolite complex is Proterozoic in age, but the skutterudite mineralization postdates the host rocks.

Locality: Tamdrost Mine, Bou Azzer Mining District, 30 km south of Tazenakht, central Anti-Atlas Mountains, central Morocco

Photo gallery of skutterudite: