metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: yellowish-tan to white; Luster: vitreous to grainy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- yellowish-tan to white
- Luster
- vitreous to grainy
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Physical properties
Hardness: 7 on Mohs scale; Color: yellowish-tan to white; Luster: vitreous to grainy; Crystal structure: Trigonal (microcrystalline); Cleavage: None/Conchoidal fracture; Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the sand grains to recrystallize and fuse together. Often found in Precambrian and Paleozoic orogenic belts.
Uses & applications
Used in construction as crushed stone or decorative facing, in the manufacturing of glass and ceramics, and as a refractory material in industrial furnaces.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains themselves rather than around them. It is one of the most durable and weather-resistant rocks on Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (scratches glass/steel) and sugary/granular texture. Commonly found in mountain ranges and glacial deposits. Look for it where ancient seafloor sandstones were subjected to tectonic pressure.
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