metamorphic
Hard Sandstone (Quartzite)
Quartz-rich Sedimentary Rock (Proto-Quartzite)
Hardness: 6-7 on Mohs scale; Color: tan, grey, and reddish-brown due to iron oxide staining; Luster: earthy to dull; Structure: fine-grained clastic texture with incipient metamorphic bedding; Cleavage: none (conchoidal to irregular fracture).
- Hardness
- 6-7 on Mohs scale
- Color
- tan, grey, and reddish-brown due to iron oxide staining
- Luster
- earthy to dull
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Physical properties
Hardness: 6-7 on Mohs scale; Color: tan, grey, and reddish-brown due to iron oxide staining; Luster: earthy to dull; Structure: fine-grained clastic texture with incipient metamorphic bedding; Cleavage: none (conchoidal to irregular fracture).
Formation & geological history
Formed from the lithification of quartz sand grains, likely undergoing low-grade regional metamorphism. These rocks can date back hundreds of millions of years, often found in ancient riverbeds or coastal environments.
Uses & applications
Commonly used as crushed stone in construction, road base, and as decorative stone in landscaping. High-purity quartzites are used in glass making.
Geological facts
Sandstone can preserve fossilized ripples from ancient water currents. When sandstone is deeply buried and heated, it turns into pure quartzite, one of the toughest rocks on the planet.
Field identification & locations
Identify by its gritty texture (feels like sandpaper) and visible grains. It will not react with acid (unlike limestone) and is hard enough to scratch glass if it has high quartz content. Found globally in mountainous and coastal regions.
