metamorphic
Quartzite
Metamorphic Rock (Mainly SiO2)
Hardness: 7 on Mohs scale; Color: Reddish-brown to tan (due to iron oxide staining); Luster: Vitreous to dull; Crystal structure: Granular/Crystalline; Cleavage: None; Specific Gravity: 2.6-2.7
- Hardness
- 7 on Mohs scale
- Color
- Reddish-brown to tan (due to iron oxide staining)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: Reddish-brown to tan (due to iron oxide staining); Luster: Vitreous to dull; Crystal structure: Granular/Crystalline; Cleavage: None; Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure. The original sand grains recrystallize into a dense, interlocking mosaic of quartz. This specimen shows significant rounding from water erosion (conglomerate/river cobble).
Uses & applications
Used in construction as crushed stone for road gravel and railway ballast. High-purity quartzite is used to produce ferrosilicon, industrial silica sand, and glass. Also used as a decorative stone in landscaping.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the ridges and peaks of mountain ranges. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness, granular 'sugary' texture on fresh breaks, and absence of reaction to acid. Commonly found in metamorphic belts and as rounded cobbles in ancient riverbeds.
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