Fayalite
Fayalite is named after its discovery locality, on Fayal Island, Azores; although believed to occur in the local lavas. Fayalite is iron-bearing olivine mineral.
Fayalite is very rare in nature, but common in man-made (metallurgy) iron slags.
Fayalite is very rare in nature, but common in man-made (metallurgy) iron slags.
| General Information | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| A variety or type of: | Peridot | |||||||||
| Chemical Formula |
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| Physical Properties of Fayalite | ||||||||||
| Mohs Hardness | 6.5 to 7, Handbook of mineralogy (2001) | |||||||||
| Specific Gravity | 4.392, Handbook of mineralogy (2001) | |||||||||
| Tenacity | Brittle, Handbook of mineralogy (2001) | |||||||||
| Cleavage Quality | Imperfect, Handbook of mineralogy (2001) | |||||||||
| Fracture | Conchoidal, Handbook of mineralogy (2001) | |||||||||
| Optical Properties of Fayalite | ||||||||||
| Refractive Index | 1.827 to 1.879, Handbook of mineralogy (2001) | |||||||||
| Optical Character | Biaxial/-, Handbook of mineralogy (2001) | |||||||||
| Pleochroism | Faint: pale yellow - yellow-orange, reddish brown., Handbook of mineralogy (2001) | |||||||||
| Dispersion | Weak, Handbook of mineralogy (2001) | |||||||||
| Colour | ||||||||||
| Colour (General) | Greenish yellow, yellow-brown, brown; pale yellow to amber in thin section, Handbook of mineralogy (2001) | |||||||||
| Transparency | Transparent, Handbook of mineralogy (2001) | |||||||||
| Lustre | Vitreous,Resinous, Handbook of mineralogy (2001) Vitreous to resinous on fractures | |||||||||
| Crystallography of Fayalite | ||||||||||
| Crystal System | Orthorhombic, Handbook of mineralogy (2001) | |||||||||
| Habit | Crystals are thick to thin, tabular, typically with wedge-shaped terminations, producing eight-sided cross sections. Commonly granular, compact, or massive., Handbook of mineralogy (2001) | |||||||||
| Geological Environment | ||||||||||
| Where found: | In ultramafic volcanic and plutonic rocks, less commonly in felsic plutonic rocks; rarely in granite pegmatite; in lithophysae in obsidian. In metamorphosed iron-rich sediments and impure carbonate rocks., Handbook of mineralogy (2001) | |||||||||
| Further Information | ||||||||||
| Mineral information: | Fayalite information at mindat.org | |||||||||