Chemical Formula: Ca2(Mg,Fe Al)5 (Al,Si)8O22(OH)2

Chemical Name: Calcium Magnesium Iron Aluminum Silicate Hydroxide

Mineral Class: Inosilicate

Mineral Notes: Hornblende is the name given to a series of minerals that are difficult to distinguish by ordinary means. The iron, magnesium and aluminium ions can freely substitute for each other and form what have been distinguished as seperate minerals. The minerals are given the names Magnesio-Hornblende, Ferro-Hornblende, Alumino-Ferro-Hornblende and Alumino-Magnesio-Hornblende. The iron rich members of the series are darker black and less likely to be transparent. Good crystals are difficult to find. Uralite is a variety which is a Hornblende pseudomorph after Pyroxine group minerals, typically Augite.

Description: Numerous prismatic crystals of Uralite bonded together into the body of the specimen. These have the very clearly defined form of Augite, which was later replaced by the Hornblende. The crystals have green colour and a silk-like luster.

Location: Calumet Iron Mine, Chaffee Co., Colorado, USA.