metamorphic
Quartzite
Quartzite (primarily SiO2)
Hardness: 7 on Mohs scale; Color: yellowish-tan to greyish-white; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: none (conchoidal fracture).
- Hardness
- 7 on Mohs scale
- Color
- yellowish-tan to greyish-white
- Luster
- vitreous to dull
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Physical properties
Hardness: 7 on Mohs scale; Color: yellowish-tan to greyish-white; Luster: vitreous to dull; Crystal structure: Trigonal/Hexagonal (granular); Cleavage: none (conchoidal fracture).
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. Geological age can range from Precambrian to recent.
Uses & applications
Used in construction as crushed stone or decorative facing, in the manufacturing of glass and ceramics, and as a durable material for kitchen countertops.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks during erosion, often forming the tops of ridges and hills. It is harder than steel and can easily scratch glass.
Field identification & locations
Identify in the field by its hardness (it will scratch a steel knife) and its grainy, sugary appearance on fresh breaks. It is found in mountain belts worldwide, such as the Appalachians or the Alps.
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