mineral

Quartz (Smoky/Milky variety)

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: cloudy white to yellowish-brown, Luster: Vitreous, Crystal structure: Trigonal (Hexagonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified April 2, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: cloudy white to yellowish-brown, Luster: Vitreous, Crystal structure: Trigonal (Hexagonal), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Formation & geological history

Formed through hydrothermal processes or magmatic crystallization. Quartz is common in igneous rocks like granite, metamorphic rocks like quartzite, and sedimentary sands. This specific pebble appears water-worn from a stream or river bed.

Uses & applications

Used in glass manufacturing, electronics (piezoelectric properties), abrasives, and as a semi-precious gemstone in jewelry.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. It is extremely resistant to chemical and physical weathering, which is why it often survives as rounded pebbles in rivers long after other minerals have eroded.

Field identification & locations

Identify in the field by its hardness (it will scratch glass and steel knife blades) and its lack of cleavage. Found globally in almost every geological environment. Look for smooth, translucent pebbles in stream beds.