metamorphic
Quartzite Pebble
Metamorphosed Quartz Sandstone (SiO2)
Hardness: 7 (Mohs scale), Color: Yellowish-brown (tan/buff), Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6 – 2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: Yellowish-brown (tan/buff), Luster: Vitreous to waxy, Crystal structure: Trigonal/Hexagonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6 – 2.7
Formation & geological history
Formed through the metamorphism of quartz-rich sandstone. High heat and pressure cause the sand grains to recrystallize and fuse together. This specific specimen has been further shaped into a 'river pebble' through water erosion over long periods.
Uses & applications
Used in construction as crushed stone or gravel, as high-purity silica for glassmaking, in landscaping, and occasionally as decorative stones or lapidary material.
Geological facts
Quartzite is so tough that it often outlasts the surrounding rocks in a landscape, leading to it forming ridges or occurring as durable pebbles in riverbeds far from its source. It is harder than steel and will easily scratch glass.
Field identification & locations
Identify in the field by its extreme hardness (cannot be scratched by a knife) and its grainy, sugary texture on freshly broken surfaces. Found frequently in riverbeds, glacial deposits, or mountainous regions.
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