metamorphic
Quartzite Cobble
Quartzite (primarily SiO2)
Hardness: 7 (Mohs scale), Color: tan to creamy white with dark surface staining, Lustre: vitreous to dull, Crystal structure: granular/microcrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.6-2.7
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Physical properties
Hardness: 7 (Mohs scale), Color: tan to creamy white with dark surface staining, Lustre: vitreous to dull, Crystal structure: granular/microcrystalline, Cleavage: none (conchoidal fracture), Specific gravity: 2.6-2.7
Formation & geological history
Formed from the metamorphism of quartz sandstone under intense heat and pressure. This specific specimen has been rounded and smoothed by water transport in a river or glacial environment.
Uses & applications
Commonly used in construction as crushed stone, road ballast, and decorative landscaping. High-purity quartzite is used to produce silica sand for glassmaking.
Geological facts
Quartzite is so hard that it can scratch glass and steel. Most 'river rocks' found in gravel pits are quartzites due to their extreme durability against erosion.
Field identification & locations
Identify in the field by its hardness and granular, sugary appearance on a fresh break. Commonly found in riverbeds, glacial deposits, and mountain ranges globally.
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