metamorphic
Red Quartzite
Quartzite (SiO2 with iron oxide impurities)
Hardness: 7 Mohs scale. Color: Grainy reddish-pink to deep burgundy. Lustre: Vitreous to dull. Structure: Non-foliated, granoblastic. Cleavage: Indistinct (breaks across grains). Specific Gravity: Approximately 2.65.
- Hardness
- 7 Mohs scale
- Color
- Grainy reddish-pink to deep burgundy
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Physical properties
Hardness: 7 Mohs scale. Color: Grainy reddish-pink to deep burgundy. Lustre: Vitreous to dull. Structure: Non-foliated, granoblastic. Cleavage: Indistinct (breaks across grains). Specific Gravity: Approximately 2.65.
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. Under high heat and pressure, sand grains recrystallize and fuse into a solid rock. The red color is typically due to the presence of hematite or other iron oxides during formation.
Uses & applications
Used extensively in construction as road ballast, railway track bedding, and foundation stone. In polished form, it is used for countertops, floor tiles, and decorative stonework. It is also used in the manufacture of glass and industrial abrasives.
Geological facts
Quartzite is so hard and durable that it often forms the crests of mountain ridges because it resists weathering better than the surrounding rock. It is often mistake for granite, but unlike granite, it lacks dark mica or amphibole flecks.
Field identification & locations
Identify in the field by its sugary, granular texture and its ability to easily scratch glass and steel. It does not react to acid. Common in ancient shield areas like the Lake Superior region and the Appalachians. Collectors should look for specimens with interesting color banding or sparkle.
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