metamorphic
Quartzite
Quartzite (SiO2)
Hardness: 7 (Mohs scale), Color: tan to creamy-yellow with iron staining, Luster: vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture)
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to creamy-yellow with iron staining, Luster: vitreous to dull, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture)
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events. This specimen shows signs of alluvial weathering.
Uses & applications
Used in construction as road aggregate, railroad ballast, and decorative stone. High-purity quartzite is also used to produce silica sand for glass making.
Geological facts
Quartzite is so hard that it can easily scratch glass and even high-quality steel. It is often more resistant to weathering than the surrounding rock, leading to the formation of ridges and hilltops.
Field identification & locations
Identified in the field by its sugary texture and extreme hardness. Common in mountainous regions. Unlike limestone, it will not fizz with acid.
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