Quartz (Commonly referred to as a River Rock or Quartzite Pebble)

Hardness: 7 (Mohs scale), Color: tan, white, and translucent gray, Luster: Vitreous to waxy, Crystal Structure: Trigonal/Hexagonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formed primarily through the crystallization of magma or by the precipitation of hydrothermal solutions. This specific specimen appears to be water-worn, smoothed by transport in a river or stream over thousands of years. It may also be a piece of quartzite formed from the metamorphism of sandstone.

Used in construction as a base material, in glassmaking, and as an abrasive. Smooth river stones are popular in landscaping, aquarium decor, and as 'worry stones' for collectors.

Quartz is the second most abundant mineral in Earth's continental crust. Its name comes from the Greek word 'krustallos', meaning ice, because ancient Greeks believed quartz was ice that had frozen so hard it would never melt.

Identify in the field by its hardness (it will scratch glass) and its lack of cleavage. Common in riverbeds, beaches, and mountain trails. Collectors should look for unique banding or internal inclusions.