metamorphic
Quartzite Pebble
Quartzite (composed primarily of SiO2)
Hardness: 7 (Mohs scale); Color: Tan, beige, or yellowish-green; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: approx. 2.65.
- Hardness
- 7 (Mohs scale)
- Color
- Tan, beige, or yellowish-green
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, beige, or yellowish-green; Luster: Vitreous to dull; Crystal structure: Non-foliated, granular; Cleavage: None; Specific gravity: approx. 2.65.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, causing the quartz grains to recrystallize into a dense, interlocking mosaic of crystals. This specimen displays significant rounding from water erosion, likely in a river or beach environment.
Uses & applications
Used in construction as a sturdy decorative stone, as railway ballast, and in the manufacturing of glass and ceramics due to its high silica content. Smooth pebbles are often used in landscaping or as pocket stones.
Geological facts
Quartzite is so hard that it will scratch glass and even high-grade steel. It is more resistant to weathering than the original sandstone from which it formed, often appearing as outcrops on ridge tops.
Field identification & locations
Identify by its extreme hardness and grainy, sugary texture on fresh surfaces. This specific piece is a 'river rock' or 'tumble' characterized by its smooth, ellipsoidal shape. Commonly found in areas with ancient mountain belts or active river systems.
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