metamorphic
Quartzite Pebble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs); Color: Tan, brown, white, and reddish-pink hues; Luster: Dull to vitreous; Crystal Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
- Hardness
- 7 (Mohs)
- Color
- Tan, brown, white, and reddish-pink hues
- Luster
- Dull to vitreous
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Physical properties
Hardness: 7 (Mohs); Color: Tan, brown, white, and reddish-pink hues; Luster: Dull to vitreous; Crystal Structure: Granular/Microcrystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone. Under intense heat and pressure, quartz grains recrystallize and fuse together. This specific specimen has been further smoothed by fluvial or glacial erosion.
Uses & applications
Used in construction as crushed stone, for railway ballast, and occasionally in glassmaking or as sandpaper grit. Naturally tumbled pebbles are popular for landscaping and decorative aquariums.
Geological facts
Quartzite is so tough that it often outlasts the surrounding softer rocks, leading to the formation of prominent ridges and peaks in mountain ranges. It is harder than a steel knife blade.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and its granular, sugary texture. Common in riverbeds, glacial deposits, and mountain outcrops globally.
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