metamorphic
Quartzite Pebble
Quartzite (SiO2)
Hardness: 7 on the Mohs scale; Color: Tan, yellowish-brown to white; Luster: Vitreous to waxy; Structure: Granoblastic, microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on the Mohs scale
- Color
- Tan, yellowish-brown to white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on the Mohs scale; Color: Tan, yellowish-brown to white; Luster: Vitreous to waxy; Structure: Granoblastic, 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, typically in orogenic belts. This specific specimen has been further shaped into a rounded pebble by fluvial or coastal erosion.
Uses & applications
Commonly used in construction as crushed stone or road ballast, as abrasive material, and as ornamental landscaping stone. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so durable that it often survives multiple cycles of erosion and deposition. It is harder than steel, meaning a steel knife blade will typically leave a metal mark on the rock rather than scratching it.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and its sugary, crystalline texture that breaks through the grains rather than around them. Found globally in ancient mountain ranges and beach deposits.
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