metamorphic
Quartzite Pebbles
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: varies from white, cream, to yellowish-tan; Luster: vitreous to waxy; Structure: non-foliated, granular; Cleavage: none, conchoidal fracture; Specific gravity: approx 2.65.
- Hardness
- 7 on Mohs scale
- Color
- varies from white, cream, to yellowish-tan
- Luster
- vitreous to waxy
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Physical properties
Hardness: 7 on Mohs scale; Color: varies from white, cream, to yellowish-tan; Luster: vitreous to waxy; Structure: non-foliated, granular; Cleavage: none, conchoidal fracture; Specific gravity: approx 2.65.
Formation & geological history
Formed from the metamorphism of quartz sandstone under high heat and pressure, where quartz grains recrystallize into a dense network. These specific specimens are water-worn river or beach pebbles.
Uses & applications
Used extensively in construction as aggregate, in glass manufacturing, and as decorative landscaping stones or aquarium gravel. Dense varieties are used as grinding media.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the cap of mountains or ridges because it erodes much slower than surrounding rocks. It can be distinguished from sandstone because it breaks across the quartz grains rather than around them.
Field identification & locations
Identify in the field by its high hardness (it will scratch glass) and lack of reaction to acid. Often found in riverbeds, glacial tills, or high-energy beach environments. Look for the distinctive sugary texture upon breaking.
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