metamorphic
Quartzite (specifically Milky Quartz variety)
Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Milky white to pale green/yellow; Luster: Vitreous to greasy; Crystal Structure: Hexagonal (trigonal); Cleavage: Poor/Conchoidal fracture; Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Milky white to pale green/yellow
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale; Color: Milky white to pale green/yellow; Luster: Vitreous to greasy; Crystal Structure: Hexagonal (trigonal); Cleavage: Poor/Conchoidal fracture; Specific Gravity: 2.65
Formation & geological history
Formed from the metamorphism of quartz-rich sandstone or through hydrothermal veins where fluids deposit silica in rock fractures over millions of years.
Uses & applications
Used as an abrasive, in glass making, as a gemstone (aventurine or milky quartz variants), and as a decorative stone in landscaping and construction.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Milky quartz gets its cloudy appearance from tiny fluid inclusions of gas or liquid trapped during crystal growth.
Field identification & locations
Identify by its inability to be scratched by a steel knife, its characteristic conchoidal (shell-like) fracture, and lack of reaction to acid. Common globally in mountain ranges and riverbeds.
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