metamorphic
Quartzite (Iron-stained)
Quartzite (mostly SiO2)
Hardness: 7 on Mohs scale (scratches glass). Color: Tan, beige, and reddish-brown due to iron oxide staining. Luster: Vitreous to dull. Crystal structure: Non-foliated, granular. Specific gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale (scratches glass)
- Color
- Tan, beige, and reddish-brown due to iron oxide staining
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale (scratches glass). Color: Tan, beige, and reddish-brown due to iron oxide staining. Luster: Vitreous to dull. Crystal structure: Non-foliated, granular. Specific gravity: 2.6-2.7.
Formation & geological history
Formed through the regional metamorphism of quartz sandstone. High heat and pressure caused the original quartz grains to recrystallize and fuse together. The iron-staining suggests it was exposed to oxygenated groundwater during or after formation.
Uses & applications
Used widely in construction as road ballast, railroad tracks, and roofing granules. Polished stones of this quality are sometimes used in landscaping or as decorative garden stones.
Geological facts
Quartzite is so durable that it often survives intense weathering that destroys other rocks. It is frequently found as rounded cobbles in riverbeds, having been transported long distances from its source ledge.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its sugary or grainy texture. It will not fizz with acid, distinguishing it from marble. Common in mountain ranges and glacial till.
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