metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or milky white; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or milky white
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or milky white; Luster: Vitreous to waxy; Crystal structure: Trigonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65
Formation & geological history
Formed from the metamorphism of quartz starch sandstone through intense heat and pressure, typically in convergent plate boundaries. This specific specimen has been further shaped into a smooth pebble by river or coastal erosion (rounded via fluvial transport).
Uses & applications
Commonly used in construction as crushed stone or gravel, in landscaping for decoration, and as a raw material for silica in glass manufacturing. Smooth river pebbles are often used in interior design and aquariums.
Geological facts
Quartzite is so hard that it will scratch window glass and steel. It is frequently more durable than the mountains it forms, often remaining as ridge caps long after other rocks have eroded away.
Field identification & locations
Identify in the field by its extreme hardness, lack of fizzing with acid (distinguishing it from limestone), and its grainy, sandpaper-like texture that appears fused together. Usually found in riverbeds, glacial tills, and mountain ranges.
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