metamorphic
Quartzite
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: Grayish-white to tan, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Grayish-white to tan, Luster: Vitreous to dull, Crystal Structure: Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This specimen has been rounded and smoothed by water erosion.
Uses & applications
Used as decorative stone, crushed stone for road construction, railway ballast, and in the manufacturing of glass and ceramics due to its high silica content.
Geological facts
Quartzite is one of the most durable rocks on Earth. Because it is so hard, it often forms the resistant caps of high ridges and mountains. It is harder than steel and will scratch a glass plate easily.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness. Commonly found in riverbeds, glacial tills, and ancient mountain ranges. It will not react with acid, distinguishing it from marble.
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