metamorphic
Quartzite (Yellow/Tan river stone variety)
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale (scratches glass). Color: Tan, yellowish-brown, or grey. Luster: Vitreous to waxy. Crystal Structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
- Hardness
- 7 on Mohs scale (scratches glass)
- Color
- Tan, yellowish-brown, or grey
- Luster
- Vitreous to waxy
Identified More metamorphic →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 7 on Mohs scale (scratches glass). Color: Tan, yellowish-brown, or grey. Luster: Vitreous to waxy. Crystal Structure: Hexagonal (microcrystalline). Cleavage: None (conchoidal fracture). Specific Gravity: 2.6-2.7.
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, usually during mountain-building events. The rounded shape indicates significant water erosion/transport in a river or glacial environment.
Uses & applications
Used as a decorative stone in landscaping, a durable aggregate for construction, and historically as a material for stone tools or 'strike-a-lights' for fire making.
Geological facts
Quartzite is so durable that it often remains as resistant ridges or 'caprock' in mountain ranges long after softer rocks have eroded away. It is tougher than the sandstone from which it originated because the quartz grains have fused together.
Field identification & locations
Identify by its extreme hardness (cannot be scratched by a steel knife) and its grainy, 'sugary' texture on a fresh break. Common in riverbeds and glacial tills globally. It feels heavier and denser than common sandstone.
More like this
