metamorphic
Quartzite pebble with Quartz and Mica
Metamorphic Quartzite (SiO2 with accessory minerals)
Hardness: 7 on Mohs scale; Color: Grayish-white with dark bluish-gray and yellowish streaks; Luster: Vitreous to dull; Structure: Granoblastic, fine- to medium-grained; Cleavage: None (conchoidal to uneven fracture).
- Hardness
- 7 on Mohs scale
- Color
- Grayish-white with dark bluish-gray and yellowish streaks
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Grayish-white with dark bluish-gray and yellowish streaks; Luster: Vitreous to dull; Structure: Granoblastic, fine- to medium-grained; Cleavage: None (conchoidal to uneven fracture).
Formation & geological history
Formed through the regional metamorphism of quartz-rich sandstone under intense heat and pressure, often reshaped and rounded into pebbles by alluvial or coastal water erosion.
Uses & applications
Used as aggregate in construction, landscaping stones, railway ballast, and decorative beach or river pebbles.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering. When sandstone metamorphoses into quartzite, individual quartz grains recrystallize along with former cementing material to form an interlocking mosaic of quartz crystals.
Field identification & locations
Identified in the field by its extreme hardness (scratches glass and steel), sugary or granular texture, and lack of reaction to acid. Commonly found along riverbeds, beaches, and glacial deposits.
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