metamorphic

Quartz-veined metamorphic cobble

Likely quartzite or quartz-rich metasedimentary rock; veins predominantly quartz (SiO₂)

AI-generated identification · may be incorrect

Tan-brown, rounded water-worn cobble with white-gray, glassy quartz veins and darker mineral bands. Quartz hardness is 7 Mohs; the host may be ~5–7, with massive texture, no obvious cleavage, and moderate-to-high density (~2.6–2.8 g/cm³).

Identified September 2, 2026More metamorphic →

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Physical properties

Formation & geological history

Probably derived from sandstone or another sedimentary protolith that was metamorphosed, fractured, and invaded by silica-rich fluids; later erosion rounded it in a stream or glacial deposit. Exact age and locality cannot be determined from the image.

Uses & applications

Primarily a collected or decorative stone; durable quartz-rich material can be used as aggregate, landscaping stone, or occasionally lapidary material, though this specimen is not gem-grade.

Geological facts

The contrasting pale veins are likely quartz filling fractures, while the brown color may reflect iron-oxide staining. A streak, hardness, and acid test would help distinguish quartzite from other quartz-veined rocks.

Field identification & locations

Look for quartz that scratches glass and does not react with dilute hydrochloric acid; quartzite shows fused grains, whereas a quartz vein may fracture separately from its host. Common in mountain belts, river gravels, and glacial deposits.