Quartzite Pebble

Hardness of 7 on the Mohs scale; typically pink, reddish-brown, white, or gray; vitreous to greasy luster; non-foliated massive crystal structure with interlocking quartz grains; no cleavage; specific gravity around 2.65.

Formed through the metamorphism of quartz-rich sandstone or chert under high temperatures and tectonic pressure, commonly over millions of years in regional or contact metamorphic environments.

Used in construction, railroad ballast, manufacturing of silica bricks, decorative landscaping, and occasionally polished for ornamental jewelry.

Quartzite is extremely durable and resistant to chemical weathering, which is why quartz-rich sandstone protoliths survive as resistant pebbles and boulders (such as beach pebbles) long after other rocks have eroded away. The distinctive reddish patch on this specific pebble is likely due to iron oxide (hematite) staining.

Can be identified in the field by its high hardness (scratches glass easily), the lack of visible individual sand grains fracturing around grain boundaries (it breaks across the grains rather than around them), and smooth rounded shape from wave action. Found globally in ancient riverbeds, beaches, and mountain ranges.