White Quartzite

Hardness: 7 (Mohs scale); Color: White to light gray; Luster: Vitreous to dull; Crystal structure: Trigonal/Hexagonal (in parent quartz); Cleavage: None (conchoidal fracture); Granular texture.

Formed through the metamorphism of quartz-rich sandstone. Under intense heat and pressure from tectonic activity, the individual quartz grains recrystallize and fuse together into a dense, interlocking structure. It is found in mountain belts worldwide and can date from the Precambrian to more recent geological eras.

Used widely in construction as crushed stone for road grit and railway ballast. Due to its resistance to weathering and high silica content, it is also used in the manufacturing of glass, ceramics, and as a decorative stone in landscaping or interior design.

Quartzite is so tough that it often outlasts the surrounding softer rocks, forming prominent ridges and peaks. It is often confused with marble, but unlike marble, quartzite will not react with acid and is much harder (quartzite scratches glass, marble does not).

Identify in the field by its extreme hardness and sugary, granular appearance. It typically breaks across the grains rather than around them. Common in the Appalachian Mountains, Alps, and Lake Superior region. Collectors look for pieces with interesting inclusions or high purity.