metamorphic
Quartzite river pebble
Quartzite (principally SiO2)
Hardness: 7 (Mohs scale); Color: Light grey to buff with minor iron staining; Luster: Dull to vitreous; Crystal structure: Granoblastic (microcrystalline); Cleavage: None (conchoidal fracture)
- Hardness
- 7 (Mohs scale)
- Color
- Light grey to buff with minor iron staining
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs scale); Color: Light grey to buff with minor iron staining; Luster: Dull to vitreous; Crystal structure: Granoblastic (microcrystalline); Cleavage: None (conchoidal fracture)
Formation & geological history
Formed via the metamorphism of quartz-rich sandstone subjected to high heat and pressure. The pebble shape indicates it was later eroded and moved by water, creating its rounded, smooth texture.
Uses & applications
Primarily used as crushed stone in construction, road ballast, or as decorative landscaping stones. In ancient times, it was used for stone tools.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caps of ridges and mountains because it resists weathering better than surrounding rocks.
Field identification & locations
Identify in the field by its extreme hardness (will scratch glass easily) and its tendency to break across sand grains rather than around them. Commonly found in riverbeds and glacial deposits.
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