metamorphic
Fuchsite Gneiss (Green Quartzite)
Chromium-rich Muscovite (KAl2(AlSi3O10)(OH)2 with Cr replacements)
Hardness: 6-7 (if quartz-heavy) or 2-3 (if pure mica); Color: Emerald green to silvery-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect basal.
- Hardness
- 6-7 (if quartz-heavy) or 2-3 (if pure mica)
- Color
- Emerald green to silvery-green
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 6-7 (if quartz-heavy) or 2-3 (if pure mica); Color: Emerald green to silvery-green; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect basal.
Formation & geological history
Formed through regional metamorphism of clay-rich sediments or ultra-mafic rocks where chromium is present. The green color is derived from small amounts of trivalent chromium replacing aluminum in the mica structure.
Uses & applications
Used primarily as an ornamental stone, in the production of 'Green Aventurine' jewelry when included in quartz, and as a collector's specimen.
Geological facts
Fuchsite is often associated with gold deposits; in some regions, it is known as 'Mariposite' when appearing in dolomitic marble. It is the chromium variety of common muscovite mica.
Field identification & locations
Identify by its distinct emerald-green flaky appearance and its tendency to sparkle (micaceous luster). Commonly found in Precambrian metamorphic terrains, especially in Brazil, India, and Russia.
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