metamorphic
Quartzite
Metamorphic Quartz (SiO2)
Hardness: 7 on Mohs scale; Color: yellowish-tan to grey; Luster: vitreous to dull (weathered); Crystal structure: Trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- yellowish-tan to grey
- Luster
- vitreous to dull (weathered)
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: yellowish-tan to grey; Luster: vitreous to dull (weathered); Crystal structure: Trigonal (microcrystalline); Cleavage: none; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically in convergent plate boundaries. The specimen shown appears stream-rounded or beach-worn.
Uses & applications
Used in construction as road ballast, in glass manufacturing, and often as decorative landscaping stones or garden pebbles.
Geological facts
Quartzite is so tough that it often survives intense erosion that wears away surrounding softer rocks. It can be distinguished from sandstone because it breaks through the quartz grains rather than around them.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its grainy but crystalline appearance. Commonly found in mountain belts and river beds draining metamorphic terrains.
