metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: Gray, white, or tan with possible reddish staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Gray, white, or tan with possible reddish staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Gray, white, or tan with possible reddish staining; Luster: Vitreous to dull; Crystal structure: Non-foliated, granoblastic; Cleavage: None (conchoidal fracture); Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events. The original quartz sand grains recrystallize into an interlocking mosaic.
Uses & applications
Used in construction as crushed stone or decorative building stone, in the production of glass and ceramics, and as a durable material for countertops and flooring.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than around them, which is a key differentiator from sandstone. It is highly resistant to chemical weathering and creates prominent ridges in mountainous terrain.
Field identification & locations
Identify in the field by its extreme hardness (will scratch glass) and its sugary, granular appearance. Commonly found in folded mountain belts globally. For collectors, it is valued for its durability and various pastel tints.
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