metamorphic
Yellow Quartzite (River Cobble)
Quartzite (SiO2 with iron oxide staining)
Hardness: 7 (Mohs scale), Color: Cream to yellow-orange due to limonitic staining, Luster: Vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
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Physical properties
Hardness: 7 (Mohs scale), Color: Cream to yellow-orange due to limonitic staining, Luster: Vitreous to waxy, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific gravity: 2.65
Formation & geological history
Formed from the metamorphism of quartz-rich 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
Used as decorative garden stone, in construction aggregates, or as a source of high-purity silica for glass manufacturing.
Geological facts
Quartzite is so tough that it often survives millions of years of erosion, eventually becoming the rounded cobbles found in riverbeds. It is harder than steel and will easily scratch a glass plate.
Field identification & locations
Identify by its extreme hardness and sugary, crystalline texture when broken. Commonly found in riverbeds or glacial tills. It is more durable than marble and does not fizz with acid.
