metamorphic
Quartzite river pebble
Quartzite (SiO2)
Hardness: 7 on Mohs scale; Color: tan, grey, cream; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline quartz); Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- tan, grey, cream
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, grey, cream; Luster: vitreous to dull; Crystal structure: hexagonal (microcrystalline quartz); Cleavage: none (conchoidal fracture).
Formation & geological history
Forms from the metamorphism of quartz-rich sandstone under intense heat and pressure. This specimen has been rounded and smoothed by fluvial (river) erosion.
Uses & applications
Commonly used as construction aggregate, railway ballast, and decorative landscaping stone. Dense, high-quality quartzite is used in glassmaking.
Geological facts
Quartzite is so durable that it often survives through multiple cycles of erosion and deposition. It is often harder than the steel blade of a pocket knife.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Commonly found in riverbeds and glacial deposits.
