metamorphic
Quartzite (Aventurine type)
Metamorphosed Quartz Sandstone (SiO2 with inclusions)
Hardness: 7 (Mohs scale); Color: Reddish-brown with sparkling inclusions; Luster: Vitreous to shimmering; Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture)
- Hardness
- 7 (Mohs scale)
- Color
- Reddish-brown with sparkling inclusions
- Luster
- Vitreous to shimmering
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Physical properties
Hardness: 7 (Mohs scale); Color: Reddish-brown with sparkling inclusions; Luster: Vitreous to shimmering; Structure: Granular/Crystalline; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed when quartz-rich sandstone is subjected to intense heat and pressure (metamorphism). The sparkly appearance, known as aventurescence, is usually caused by platy mineral inclusions like mica or hematite.
Uses & applications
Commonly used as a decorative stone, in landscaping, as a construction aggregate, and occasionally for lapidary work or semi-precious jewelry if highly translucent.
Geological facts
Quartzite is one of the most durable rocks on Earth's surface. The 'glitter' effect seen in this specimen is often called aventurescence, a optical phenomenon found in some quartz-based minerals.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, sandpaper-like visual texture that doesn't rub off. Often found in glaciated regions or ancient mountain belts.
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