metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: tan, white, gray with dark inclusions; Luster: vitreous to dull; Crystal Structure: trigonal (granular); Cleavage: none; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- tan, white, gray with dark inclusions
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: tan, white, gray with dark inclusions; Luster: vitreous to dull; Crystal Structure: trigonal (granular); Cleavage: none; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specimen shows significant river-wear or glacial rounding.
Uses & applications
Used in construction as crushed stone for road ballast, as a decorative stone in landscaping, and occasionally in glass manufacturing if high purity is present.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the peaks of hills and mountains. It is harder than a steel knife and will scratch glass easily.
Field identification & locations
Identify in the field by its extreme hardness and granular, sugary texture on fresh breaks. It is commonly found in metamorphic crystalline shields and mountain ranges. This smooth cobble is typical of riverbed finds.
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