metamorphic
Quartzite (River-worn)
Metamorphic rock predominantly composed of Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, brown, and grey with translucent edges; Luster: Waxy to vitreous; Structure: Granular/crystalline; Specific Gravity: 2.6-2.7. Extremely durable and resists scratching.
- Hardness
- 7 on Mohs scale
- Color
- Tan, brown, and grey with translucent edges
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, brown, and grey with translucent edges; Luster: Waxy to vitreous; Structure: Granular/crystalline; Specific Gravity: 2.6-2.7. Extremely durable and resists scratching.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the original quartz grains to recrystallize. This specific specimen has been rounded by fluvial (river) erosion over thousands of years.
Uses & applications
Commonly used in construction as crushed stone or ballast. High-quality specimens are used for lapidary work, cabochons, and decorative landscaping.
Geological facts
Quartzite is so tough that it often survives intense weathering that destroys other rocks. It can be distinguished from sandstone because it fractures through the grains, whereas sandstone fractures around them.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife, its sugary crystalline appearance, and smooth, water-worn texture when found near riverbeds or glacial deposits.
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