Quartzite

Hardness: 7 (Mohs scale), Color: White to tan with iron staining, Luster: Vitreous to waxy, Crystal Structure: Trigonal (microcrystalline), Cleavage: None/Conchoidal fracture, Specific Gravity: 2.63-2.65

Formed through the metamorphism of quartz sandstone under high heat and pressure, causing the original quartz grains to recrystallize into an interlocking mosaic of quartz crystals. Formed in various geological ages during mountain-building events.

Used as crushed stone for road construction and railroad ballast, in glass manufacturing, as dimension stone for counter tops and flooring, and occasionally as a low-value lapidary material.

Quartzite is so tough that it often outlasts the surrounding rock in weathering processes, forming prominent ridges and peaks. It is frequently mistaken for quartz crystals or white marble, but unlike marble, it will not react with acid.

Identify by its ability to scratch glass and its lack of reaction to dilute hydrochloric acid. Commonly found in metamorphic terrains worldwide, especially in riverbeds or near mountain ranges. Collectors look for pieces with interesting iron-oxide staining patterns.