metamorphic
Quartzite
Metamorphosed Quartz Sandstone
Hardness: 7 on the Mohs scale. Color: Typically white to gray, but can include shades of pink, red, or yellow due to iron oxide impurities. Luster: Vitreous to greasy. Crystal structure: Interlocking mosaic of quartz crystals. Cleavage: None, breaks across the grains. Specific gravity: 2.65 - 2.75.
- Hardness
- 7 on the Mohs scale
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 on the Mohs scale. Color: Typically white to gray, but can include shades of pink, red, or yellow due to iron oxide impurities. Luster: Vitreous to greasy. Crystal structure: Interlocking mosaic of quartz crystals. Cleavage: None, breaks across the grains. Specific gravity: 2.65 - 2.75.
Formation & geological history
Formed when quartz-rich sandstone is subjected to high heat and pressure, typically through tectonic compression in orogenic belts. Geological age can range from Precambrian to Cenozoic.
Uses & applications
Used in construction, as crushed stone for road bases, in manufacturing railroad ballast, for decorative landscaping, and sometimes as a decorative building stone or countertops.
Geological facts
Quartzite is extremely durable and resistant to chemical weathering, which is why mountains made of quartzite often remain as prominent ridges and peaks while surrounding softer rocks erode.
Field identification & locations
Can be identified in the field by its extreme hardness (scratches glass easily), lack of effervescence with acid, and the fact that it fractures through the quartz grains rather than around them like sandstone. Found worldwide.
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