mineral

Milky quartz with iron-oxide staining

Quartz, silicon dioxide (SiO₂), with hematite/goethite inclusions

AI-generated identification · may be incorrect

Typically hardness 7 Mohs, white to translucent, vitreous-to-waxy luster, and no cleavage; quartz has a trigonal crystal structure. The rounded specimen appears massive, with rusty brown staining and partly translucent edges.

Identified September 22, 2026More mineral →

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Physical properties

Formation & geological history

Likely formed in a hydrothermal quartz vein or cavity, where silica crystallized from hot mineral-rich fluids; iron-bearing minerals later oxidized to produce the brown-red patches. The geological age cannot be determined from the photograph and may range from Precambrian to recent depending on locality.

Uses & applications

Common quartz is used in glass, ceramics, abrasives, electronics, and engineered stone; attractive pieces are sold as cabinet specimens or lapidary material. This example has modest decorative value.

Geological facts

Milky quartz becomes cloudy when microscopic fluid inclusions, fractures, or mineral impurities scatter light. Brown coatings commonly consist of limonite, goethite, or hematite rather than quartz itself.

Field identification & locations

Identify it by its glassy translucence, lack of cleavage, conchoidal fracture, and ability to scratch ordinary glass; it should not be confused with calcite, which is softer and cleaves readily. Common worldwide in quartz veins, pegmatites, and metamorphic rocks.