Quartz (Pebble)

Hardness: 7 on Mohs scale. Color: Highly variable, but often translucent to opaque in shades of white, yellowish, reddish-brown, or grey. Luster: Vitreous to waxy. Crystal Structure: Trigonal. Cleavage: None. Specific Gravity: 2.65.

Quartz forms under a wide range of conditions, primarily from the crystallization of silica-rich magmas as an igneous mineral, precipitation from hydrothermal fluids, or recrystallization during metamorphic processes. As a very stable and hard mineral, it is also highly resistant to weathering, and therefore accumulates in sedimentary environments (like riverbeds and beaches) as sand grains and pebbles. The geological age can vary from Precambrian to recent, depending on the specific rock formation.

Quartz is extensively used in various industries: in electronics for oscillators and filters due to its piezoelectric properties, in glassmaking as a primary ingredient, in the abrasive industry (sandpaper, grinding media), and in construction (sand and gravel aggregate). Specific varieties are highly prized as gemstones (e.g., amethyst, citrine) for jewelry.

Quartz is one of the most common minerals on Earth's crust, found in a vast array of igneous, metamorphic, and sedimentary rocks. Its durability and abundance have made it a cornerstone in human technological and artistic development for millennia. Amethyst, citrine, rose quartz, and smoky quartz are all varieties of quartz distinguished by their color caused by trace impurities or irradiation.

To identify quartz in the field, look for its hardness (it scratches glass and steel), lack of cleavage, and common occurrence as sub-angular to rounded grains and pebbles in streambeds, beaches, and weathered rock outcrops. The presence of conchoidal (shell-like) fracture is also characteristic. Its relative transparency and often glassy luster can help differentiate it from other common pebbles. It is found globally in almost all rock types and sedimentary deposits.