metamorphic
Quartzite with Calcite Accretion
Metamorphosed Quartz Sandstone (SiO2 with CaCO3 coating)
Hardness: 7 (base rock); Color: Brownish-tan with white crust; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal
- Hardness
- 7 (base rock)
- Color
- Brownish-tan with white crust
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (base rock); Color: Brownish-tan with white crust; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal; Cleavage: None/Conchoidal
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events. The white surface crust is a secondary calcite or mineral deposition from water evaporation.
Uses & applications
Quartzite is used heavily in construction as crushed stone for road gravel and as a decorative building stone. This specific piece is a common landscape or river rock.
Geological facts
Quartzite is so durable that it can outlast the mountains themselves. While the base rock is extremely hard, the white mineral crust on top will react and bubble if a drop of vinegar (weak acid) is applied.
Field identification & locations
Identify by its ability to scratch glass and its granular, sugary texture on fresh breaks. Commonly found in riverbeds, glacial tills, and mountain outcrops. Look for rounded edges indicating water transport.
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