metamorphic
Green Quartzite (or Aventurine)
SiO2 (Silicon Dioxide) primarily, with Fuchsite inclusions (K(Al,Cr)2AlSi3O10(OH)2)
Hardness: 7 on Mohs scale; Color: Pale to medium green with white/gray matrix; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (trigonal) microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 7 on Mohs scale
- Color
- Pale to medium green with white/gray matrix
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Pale to medium green with white/gray matrix; Luster: Vitreous to waxy; Crystal Structure: Hexagonal (trigonal) microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure Recrystallize the sand grains into a dense rock. The green tint is typically due to the inclusion of chromium-rich mica (fuchsite) during the metamorphic process.
Uses & applications
Used frequently in construction as decorative stone (countertops, tiles), as landscaping gravel, and in jewelry/lapidary as beads or cabochons. It is also popular in the metaphysical community.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges and hills. In its 'Aventurine' form, it displays a glittering effect known as aventurescence due to light reflecting off mica inclusions.
Field identification & locations
Identify in the field by its extreme hardness (it will easily scratch glass) and its grainy, sugary texture compared to the smooth look of chert. Commonly found in mountainous regions such as the Appalachians, Brazil, or India.
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