metamorphic

Quartzite

AI-generated identification · may be incorrect

Hardness of 7 on the Mohs scale. Colors can vary, often white to pale grey, but this specimen shows yellowish/tan hues likely from iron oxide staining. Luster is vitreous to greasy. Granular texture, composed primarily of interlocking quartz crystals. No cleavage. Specific gravity is typically 2.64-2.69.

Identified September 19, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed from quartz-rich sandstone that has been subjected to high heat and pressure (metamorphism), usually related to tectonic compression. This causes the quartz grains to recrystallize and fuse together.

Uses & applications

Used in construction as decorative stone, crushed stone for railway ballast, and in the production of silica for various industrial applications. Also polished for use as countertops and occasionally tumbled for decorative or collectible purposes.

Geological facts

Because the quartz grains are so tightly interlocked, quartzite breaks across the grains rather than around them, which is a key distinguishing feature from sandstone.

Field identification & locations

Identified by its high hardness (scratches glass), lack of reaction to acid, and crystalline, granular appearance that breaks across grains. Common worldwide in areas of past tectonic activity.