Hühnerberg, Oberpleis, Siebengebirge, North Rhine-Westphalia, Germany

(Mg,Fe)₂SiO₄

Crystal System: orthorhombic
Colour: green, pale yellow or white/greenish-yellow, yellow or brown
Lustre: vitreous
Habitus: typically as granular or compact massive aggregates. Less frequently, as euhedral or subhedral equant to prismatic crystals
Hardness: 7 
Fracture: conchoidal
Cleavage:{010}, {100}, imperfect
Density: 3.271-4.40 g/cm³
Origin and geological occurrence: the term “olivine” indicates a series between forsterite, Mg2(SiO4), and fayalite, Fe2(SiO4) [occhio ai pedici!]. Forsterite occurs in mafic and ultramafic rocks and, rarely, in metamorphosed impure dolomitic limestone. Fayalite is rarer than forsterite and occurs in several geological environments: ultramafic (less frequently also in felsic) volcanic and intrusive rocks, in granite pegmatite (rare), and in lithopysae in obsidian. Fayalite can be found in Fe-rich metasediments and impure carbonate rocks

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Smorf link

Samples:

	9A.1 Olivine Granular aggregates of “olivine” in lava #neso soro silicates
	9A.2 Olivine Anhedral grains in lava #neso soro silicates