Quartzite

Physical Properties

Hardness: 7 on Mohs scale; Color: Yellow-orange to Tan with reddish iron staining; Luster: Vitreous to waxy; Structure: Granular/crystalline; Cleavage: None (conchoidal fracture); Specific Gravity: 2.63-2.65

Formation & Geological History

Formed from the metamorphism of quartz-rich sandstone under intense heat and pressure, typically during mountain-building events. This smooth, rounded specimen was likely shaped by fluvial or glacial erosion.

Uses & Applications

Used in construction as crushed stone, for road ballast, as decorative landscaping stones, and formerly for stone tools. Higher purity varieties are used to produce silica sand for glass making.

Geological Facts

Quartzite is so tough that it often outlasts the surrounding rock, forming prominent ridges or resistant hills. It is often confused with marble, but can be distinguished because quartzite will scratch glass and marble will not.

Field Identification & Locations

Identify in the field by its hardness (scratches glass), grainy texture that breaks across grains rather than around them, and rounded river-worn shape. Commonly found in riverbeds or ancient glacial deposits.

Identified on: 5/13/2026

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