metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale); Color: Tan, yellowish-brown; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 7 (Mohs scale)
- Color
- Tan, yellowish-brown
- Luster
- Vitreous to dull
Identified More metamorphic →
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Physical properties
Hardness: 7 (Mohs scale); Color: Tan, yellowish-brown; Luster: Vitreous to dull; Crystal structure: Hexagonal (microcrystalline); 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 in convergent plate boundaries. The original quartz grains recrystallize into an interlocking mosaic.
Uses & applications
Used in construction as crushed stone or decorative facing, in the manufacturing of glass and ceramics, and as a durable material for countertops.
Geological facts
Quartzite is so hard and chemically resistant that it often forms prominent ridges and hills in landscapes, as it outlasts the softer rocks surrounding it.
Field identification & locations
Identify by its hardness (it will easily scratch glass) and lack of reaction to acid. It is commonly found in mountain belts worldwide. Collectors look for unique colors or water-worn shapes.
