mineral

Milky Quartz

Quartz (Silicon Dioxide, SiO2)

Hardness: 7 (Mohs scale), Color: White to translucent milky white, Luster: Vitreous to greasy, Crystal structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Identified June 30, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: White to translucent milky white, Luster: Vitreous to greasy, Crystal structure: Trigonal/Hexagonal, Cleavage: None (conchoidal fracture), Specific gravity: 2.65

Formation & geological history

Formed in hydrothermal veins or as a primary constituent of granites and quartzites. The milky appearance is caused by tiny inclusions of gas or liquid trapped during crystal growth. Common in Precambrian shields like that underlying the Sao Paulo region.

Uses & applications

Used in glass manufacturing, electronics (due to piezoelectric properties), construction aggregates, and as a semi-precious stone in jewelry or landscaping.

Geological facts

Milky quartz is the most common variety of crystalline quartz. It is often found as a filler in gold-bearing veins, making it an important indicator for prospectors throughout history.

Field identification & locations

Identify in the field by its hardness (will scratch glass), white streak, and lack of cleavage. In the Atlantic Forest region of Brazil (Sao Paulo), it is very common in riverbeds and as road gravel due to the erosion of ancient crystalline basement rocks.