metamorphic
Quartzite
Quartzite (Silicon Dioxide: SiO2)
Hardness: 7 (Mohs scale), Color: tan, brownish-orange, through white, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (trigonal) system, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 to 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: tan, brownish-orange, through white, Luster: Vitreous to waxy, Crystal Structure: Hexagonal (trigonal) system, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6 to 2.65
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure, typically during mountain-building events (orogeny). Its geological age can range from Precambrian to Cenozoic depending on the region.
Uses & applications
Used extensively in construction as crushed stone for road beds and railway ballast. Due to its durability, it is also used for building stone, tiles, and occasionally in jewelry as polished tumbled stones.
Geological facts
Quartzite is so hard and chemically resistant that it often forms the caprock or ridges of mountain ranges. It is frequently confused with white marble, but unlike marble, it will not fizz when exposed to acid and is harder than steel.
Field identification & locations
Identify in the field by its grainy, sugary texture and extreme hardness (it will easily scratch glass). Look for it in glaciated areas or near metamorphic mountain belts. Common in the Brazilian highlands and the Appalachian mountains.
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