metamorphic
Quartzite (with Mica/Feldspar)
Metamorphic Quartzite (SiO2 predominantly)
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: vitreous to dull, Crystal structure: granular/interlocking, Cleavage: none, Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to creamy white, Luster: vitreous to dull, Crystal structure: granular/interlocking, Cleavage: none, Specific gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz sandstone under high heat and pressure, typically during mountain-building events (orogeny). Pieces like this are often rounded by glacial or fluvial erosion.
Uses & applications
Used in construction as a decorative stone, crushed stone for road beds, and sometimes as a source of silica for glass manufacturing. Rounded specimens are often used for landscaping.
Geological facts
Quartzite is so tough that it usually breaks through the quartz grains rather than along the boundaries between them, unlike sandstone. It is one of the most durable rocks on the Earth's surface.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by steel) and lack of reaction to acid. Often found in riverbeds or glacial tills. Minor glints of mica are common in coarser metamorphic varieties.
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