Quartzite with Iron Inclusions

Hardness: 7 (Mohs scale), Color: tan, white, and reddish-brown, Luster: dull to vitreous, Crystal structure: Trigonal (granular), Cleavage: None/Conchoidal fracture, Specific gravity: 2.6-2.7

Formed through the regional metamorphism of quartz-rich sandstone. High heat and pressure cause quartz grains to recrystallize into a dense, interlocking mosaic of crystals. The reddish-brown coloration is due to the presence of iron oxide (hematite) staining.

Used in construction as road ballast, gravel, and dimension stone. Highly prized when colorful for lapidary work such as tumbling or cabochons. Chemically and physically resistant.

Quartzite is so tough that it often outlasts the surrounding rocks during erosion, frequently forming the peaks of mountains. It is harder than steel and can easily scratch a glass bottle.

Identify in the field by its grainy texture and inability to be scratched by a knife blade. Unlike sandstone, quartzite fractures through the grains rather than around them. Found globally in ancient mountain belts.