Orthoclase

Introduction: Orthoclase is a combination of two Greek words: orthos for 'right' and klas meaning 'to break'.  This refers to the mineral's two prominent right-angled cleavages. It is found in igneous rocks, syenites and some sandstones such as arkose, which has a high feldspar content.

Distribution: Common in many of Namibia's gneisses and granites.

Composition: Silicate

Crystal system: Monoclinic

Lustre: Pearly, vitreous

Streak: White

Hardness: 6-6.5