metamorphic
Quartzite pebble
Quartzite (SiO2 with iron oxide impurities)
Hardness: 7 on Mohs scale; Color: reddish-pink to brownish-orange; Luster: vitreous to sugary/dull; Crystal Structure: trigonal (interlocking quartz grains); Cleavage: none (conchoidal to irregular fracture); Specific Gravity: 2.63 - 2.65
- Hardness
- 7 on Mohs scale
- Color
- reddish-pink to brownish-orange
- Luster
- vitreous to sugary/dull
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Physical properties
Hardness: 7 on Mohs scale; Color: reddish-pink to brownish-orange; Luster: vitreous to sugary/dull; Crystal Structure: trigonal (interlocking quartz grains); Cleavage: none (conchoidal to irregular fracture); Specific Gravity: 2.63 - 2.65
Formation & geological history
Formed through the regional or contact metamorphism of quartz-rich sandstone, where intense heat and pressure recrystallize quartz grains into a dense, tightly interlocking network. The reddish hue is due to microscopic inclusions of iron oxide (hematite). Commonly eroded and rounded into pebbles by fluvial or coastal processes.
Uses & applications
Used in construction as crushed stone, railway ballast, and decorative landscaping gravel. High-purity quartzite is used in glassmaking and refractory ceramics, though water-worn pebbles are mainly collected or used decoratively.
Geological facts
Quartzite is extremely durable and resistant to both chemical weathering and physical breakdown, allowing pebbles like this to travel vast distances along rivers and ocean shores intact.
Field identification & locations
Identified by its ability to scratch glass easily, sugary granoblastic texture, and lack of reaction to acid. Commonly found along riverbeds, beaches, glacial drift deposits, and metamorphic rock outcrops globally.
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