metamorphic
Red Quartzite (Tumbled Pebble)
Quartzite (primarily SiO2 with hematite inclusions)
Hardness: 7 (Mohs scale); Color: Reddish-brown/terracotta; Luster: Vitreous to dull (waxy when tumbled); Structure: Granoblastic/Non-foliated; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
- Hardness
- 7 (Mohs scale)
- Color
- Reddish-brown/terracotta
- Luster
- Vitreous to dull (waxy when tumbled)
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Physical properties
Hardness: 7 (Mohs scale); Color: Reddish-brown/terracotta; Luster: Vitreous to dull (waxy when tumbled); Structure: Granoblastic/Non-foliated; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6 - 2.7
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. The red color is typically due to the presence of iron oxide (hematite) during the formation process.
Uses & applications
Used in landscaping, high-durability construction aggregate, railway ballast, and as a semi-precious stone for jewelry or pocket stones when polished.
Geological facts
Quartzite is so hard that it will scratch glass and even high-quality steel. In some ancient cultures, it was used to create spearheads and scrapers when chert or flint was unavailable due to its predictable fracture patterns.
Field identification & locations
Identify in the field by its inability to be scratched by a steel knife and its lack of visible individual sand grains (unlike its parent rock, sandstone). Commonly found in ancient mountain belts like the Appalachians or the Canadian Shield.
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