metamorphic
Quartzite River Pebble
Quartzite (SiO2)
Hardness: 7 (Mohs scale); Color: Grayish-tan; Luster: Dull/waxy when dry, vitreous if polished; Crystal Structure: Granular/massive; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Grayish-tan
- Luster
- Dull/waxy when dry, vitreous if polished
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Physical properties
Hardness: 7 (Mohs scale); Color: Grayish-tan; Luster: Dull/waxy when dry, vitreous if polished; Crystal Structure: Granular/massive; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure. This specific specimen has been further shaped and smoothed by fluvial (river) or coastal erosion during the Holocene era.
Uses & applications
Mainly used as decorative garden stone, landscaping material, or construction aggregate. Fine specimens may be used for lapidary tumbling.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caprock on ridges and mountains. It is harder than steel and will easily scratch glass.
Field identification & locations
Identified by its extreme hardness, granular 'sugary' texture on fresh breaks, and absence of reaction to acid. Often found in riverbeds, beaches, and glacial till globally.
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