Fayalite
Iron
Magnesium Silicate
(Fe, Mg)2SiO4
Fayalite is the iron rich end-member of the olivine solid-solution
series.
Fayalite
is from olivine group and it is one of the two minerals that are
simply called olivine. The other mineral is known as forsterite. The
mineral is named for the Island of Fayal of the Azores.
Fayalite is found in the ultramafic igneous rocks. Olivine minerals
have a high melting point and it crystallizes first from a mafic
magma. This is due to the molten lava already contain crystallized
grains of olivine.
Fayalite is sometimes also found in many iron-nickel meteorites. It
is found in significant size and somtimes even occupying over 50% of
the meteorites. Slices cut very thin from these meteorites are
extremely attractive with polished steel gray of the iron and the
embedded grains of gemmy green olivine. This effect even produces a
very close mineral being equivalent to stained glass artwork.
Pysical Properties of Fayalite
| Color |
Greenish-yellow, yellow or
brown. |
| Luster |
Vitreous |
| Transparency |
Crystals are transparent to
translucent. |
| Cleavage |
Distinct in two directions at
90 degrees. |
| Fracture |
Conchoidal |
| Hardness |
6.5 - 7 |
| Specific gravity |
Approximately 4.3 (above
average for non-metallic minerals) |
| Streak |
White |
Uses of Fayalite
- As
refractory sands
- As
abrasives
- As
mineral specimens
Associated Minerals of Fayalite
- Diopside
- Spinel
- Plagioclase
feldspars
- Chromite
- Anorthite
- Biotite
- Cristobalite
- Hornblende
- Serpentine
- Obsidian
- Iron-nickel
meteorites
- Augite
Occurrences of Fayalite
- Salt
Lake Crater and Oahu in Hawaii
- Sugarloaf
Mountain, Inyo County, california and Peridot, Gila County, and
Arizona in the USA.
- Lipari
Islands, Sicili and Mt. Vesuvius in Italy
- France
- Sweden
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