mineral

Milky Quartz Cobble

Quartz (Silicon Dioxide, SiO2)

Hardness: 7 on Mohs scale; Color: Milky white with iron staining (yellow/orange); Luster: Vitreous to greasy; Crystal Structure: Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Hardness: 7 on Mohs scale
Color: Milky white with iron staining (yellow/orange)
Luster: Vitreous to greasy

Identified June 12, 2026More mineral →

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Physical properties

Hardness: 7 on Mohs scale; Color: Milky white with iron staining (yellow/orange); Luster: Vitreous to greasy; Crystal Structure: Trigonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65

Formation & geological history

Formed through the cooling of silica-rich hydrothermal fluids in veins or as a primary mineral in igneous rocks. This specimen is a 'river rock' or 'cobble', meaning it was shaped and smoothed by water erosion over thousands of years.

Uses & applications

Used in glassmaking, as an abrasive, in electronics (due to piezoelectric properties), and for decorative landscaping or aquarium use.

Geological facts

Milky quartz gets its white, opaque appearance from tiny fluid inclusions of gas or liquid trapped during crystal growth. It is the most common variety of crystalline quartz found on Earth's crust.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its waxy or vitreous luster, and lack of cleavage planes. Found globally in river beds, beaches, and glacial deposits.