Olivine (Forsterite (Mg) and Fayalite (Fe))Mg2SiO4 - Fe2SiO4
Class: Silicate Subclass: Nesosilicate Hardness: 6.5 - 7 Density: 3.3 - 4.3 Streak: Colourless Lustre: Vitreous Habit: Granular Colours: Pistachio green, greenish yellow brown | | Crystal System: Orthorhombic Cleavage: Imperfect Fracture: Conchoidal Magnetism: None Reaction with HCl: Very weak | Identification in hand sample: Pistachio-green colour and granular habit. Associations: Mafic and ultramafic igneous rocks. Associated with Ca-plag, Industrial / ecomonic uses: Peridote (a translucent variety of olivine) is considered a 'gem' mineral. Also used as a refractory sand and infrequently as an abrasive. Comments: Complete solid solution exists between the magnesium-rich end member (Forsterite, Mg2SiO4) and the iron-rich end member (Fayalite, Fe2SiO4). |