metamorphic
Red Quartzite
Quartzite (SiO2)
Hardness: 7 on Mohs scale. Color: Salmon pink to deep rusty red due to iron oxide impurities. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None; typically displays conchoidal fracture. Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale
- Color
- Salmon pink to deep rusty red due to iron oxide impurities
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale. Color: Salmon pink to deep rusty red due to iron oxide impurities. Luster: Vitreous to dull. Crystal structure: Hexagonal (microcrystalline). Cleavage: None; typically displays conchoidal fracture. Specific Gravity: 2.6-2.7.
Formation & geological history
Quartzite forms when quartz-rich sandstone is subjected to intense heat and pressure during regional metamorphism. This process recrystallizes the quartz grains into a dense, interlocking mosaic of crystals. The red color suggests the original sandstone contained hematite or other iron minerals.
Uses & applications
Used primarily as decorative stone, crushed stone for road construction and railway ballast, and in the production of silica glass. Polished specimens are used in jewelry and lapidary art.
Geological facts
Quartzite is so tough that it often outlasts the mountain ranges it was formed in, leaving behind resistant ridges and 'monadnocks'. It is one of the most durable rocks found on the Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a steel knife) and the fact that it breaks across the quartz grains rather than around them. Commonly found in stream beds and glacial deposits worldwide.
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