Quartzite

Hardness: 7 (Mohs scale), Color: Pinkish-red due to iron oxide (hematite), Luster: Vitreous to dull, Crystal structure: Hexagonal/Trigonal (microcrystalline), Cleavage: None, Fracture: Conchoidal to irregular

Formed through the regional or contact metamorphism of quartz-rich sandstone. Under high heat and pressure, the original quartz sand grains recrystallize and fuse together. Specimens like this often show smoothing from water erosion in riverbeds or glacial transport.

Used as a decorative stone in landscaping, a durable material for construction (railway ballast, road aggregate), and occasionally as a semi-precious stone for jewelry when highly polished (often called 'pink jasper' or 'red quartzite').

Quartzite is so hard and dense that when broken, it fractures across the original grains rather than around them, unlike its parent stone, sandstone. The red and pink hues are caused by varying amounts of hematite (iron oxide) inclusions.

Identify it by its extreme hardness (it will easily scratch glass and stainless steel) and its lack of reaction to acid. Look for it in glacial till or river gravels. It is a common find in the Great Lakes region of North America and ancient mountain belts.