metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 on Mohs scale; Color: Tan, beige, or off-white; Luster: Dull to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Tan, beige, or off-white
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: Tan, beige, or off-white; Luster: Dull to vitreous; Crystal Structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure reciprocal of tectonic activity cause sand grains to recrystallize and fuse together, often in Precambrian or Paleozoic geological settings.
Uses & applications
Used as a decorative stone in landscaping, as an abrasive in industry, and as railroad ballast. Smooth river-worn specimens are often used in decorative crafts or as worry stones.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the 'caps' of mountain ridges. This specific specimen has been rounded and smoothed by water transport (river or beach action).
Field identification & locations
Identify in the field by its extreme hardness (will easily scratch glass) and lack of reaction to acid. Often found in riverbeds, glacial tills, or ancient mountain belts. Collectors look for unique colors or banding.
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