metamorphic

Weathered iron-stained quartzite or quartz-rich metamorphic cobble

Quartzite, predominantly SiO₂, with iron-oxide staining and minor mica/clay minerals

AI-generated identification · may be incorrect

Gray, massive, fine- to medium-grained, with a dull to weakly vitreous luster and rusty yellow-brown limonite/goethite patches. Quartz has Mohs hardness ~7; cleavage is absent, fracture is irregular to conchoidal, and specific gravity is about 2.6–2.7.

Identified September 2, 2026More metamorphic →

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Physical properties

Formation & geological history

Likely formed when quartz-rich sandstone recrystallized under heat and pressure during regional metamorphism, commonly Precambrian to Paleozoic in age; surface oxidation produced the iron staining. The rounded shape indicates transport as a stream or glacial cobble.

Uses & applications

Used as crushed aggregate, road stone, landscaping rock, and occasionally as a lapidary material; this specimen has little commercial value unless it displays attractive patterns when polished.

Geological facts

Quartzite is tougher and more resistant to weathering than its sandstone precursor. Iron oxides can create vivid golden, orange, or reddish veining and patches.

Field identification & locations

Identify by its glassy quartz grains, lack of obvious bedding, hardness, and inability to scratch quartz; vinegar produces no reaction. Common in metamorphic mountain belts and glacial or river gravels.