metamorphic
Quartzite
Quartzite (composed primarily of SiO2)
AI-generated identification · may be incorrectHardness: 7 on Mohs scale. Color: White, gray, reddish, or yellowish (due to iron oxide staining). Luster: Vitreous to greasy. Crystal structure: Granular. Cleavage: None. Specific gravity: 2.64-2.69.
- Hardness
- 7 on Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on Mohs scale. Color: White, gray, reddish, or yellowish (due to iron oxide staining). Luster: Vitreous to greasy. Crystal structure: Granular. Cleavage: None. Specific gravity: 2.64-2.69.
Formation & geological history
Formed through the metamorphism of pure quartz sandstone under high heat and pressure, causing the quartz grains to recrystallize and fuse together. Can be found in many geological ages.
Uses & applications
Used as decorative stone, crushed stone for road construction, railway ballast, and in the production of silica for manufacturing glass and silicon carbide.
Geological facts
Quartzite is highly resistant to chemical weathering and often forms ridges and hilltops because it is harder than surrounding rocks. The orange/red staining is typical of iron oxide (rust) from groundwater or weathering.
Field identification & locations
Identified by its hardness (scratches glass), granular sugary texture, and lack of fizzing with dilute hydrochloric acid (distinguishing it from marble). Common worldwide in metamorphic terranes. Found easily in riverbeds or beaches as smooth, water-worn pebbles.
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