metamorphic
Quartzite pebble
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: off-white to tan; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none; Fracture: conchoidal/irregular
- Hardness
- 7 on Mohs scale
- Color
- off-white to tan
- Luster
- vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 on Mohs scale; Color: off-white to tan; Luster: vitreous to dull; Crystal structure: Trigonal (microcrystalline); Cleavage: none; Fracture: conchoidal/irregular
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, causing the individual quartz grains to recrystallize into a dense interlaced structure. This specimen shows water-worn rounding.
Uses & applications
Commonly used as construction aggregate, railway ballast, and in landscaping. Polished pebbles are used in decor and as pocket stones.
Geological facts
Quartzite is so tough that it often breaks through the quartz grains rather than along the boundaries between them. It is highly resistant to chemical weathering.
Field identification & locations
Identify in the field by its hardness (will scratch glass) and lack of reaction to acid. Commonly found in riverbeds, glacial deposits, and mountain ranges. This specimen is a typical stream-rounded cobble.
