mineral
Milky Quartz in Shale
Silicon Dioxide (SiO2) in sedimentary host rock
Hardness: 7 (Quartz), 2-3 (Shale). Color: White/milky and dark gray. Luster: Vitreous to greasy for quartz, dull for shale. Structure: Hexagonal (Quartz).
- Hardness
- 7 (Quartz), 2-3 (Shale)
- Color
- White/milky and dark gray
- Luster
- Vitreous to greasy for quartz, dull for shale
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Physical properties
Hardness: 7 (Quartz), 2-3 (Shale). Color: White/milky and dark gray. Luster: Vitreous to greasy for quartz, dull for shale. Structure: Hexagonal (Quartz).
Formation & geological history
Hydrothermal veins where silica-rich fluids cooled and crystallized within fractures of existing sedimentary shale beds. Found in various geological ages.
Uses & applications
Large-scale quartz is used in glassmaking and abrasives. As a specimen, it is common for hobbyist collecting.
Geological facts
Milky quartz gets its color from tiny fluid inclusions of gas or liquid trapped during crystal growth. It is one of the most common minerals on Earth's crust.
Field identification & locations
Identify by the high hardness of the white mineral (will scratch glass) contrasting with the soft, flaky gray shale. Commonly found in road cuts and stream beds.
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