Rock Identifier
Milky Quartz with Iron Staining (Silicon Dioxide (SiO2)) — mineral
mineral

Milky Quartz with Iron Staining

Silicon Dioxide (SiO2)

Hardness: 7 on Mohs scale (cannot be scratched by steel). Color: White to off-white with yellowish-brown surface staining. Luster: Vitreous (glassy) to greasy. Crystal structure: Trigonal/Hexagonal, though rarely shows defined faces in tumbled or weathered specimens. Cleavage: Poor/None (conchoidal fracture).…

Hardness
7 on Mohs scale (cannot be scratched by steel)
Color
White to off-white with yellowish-brown surface staining
Luster
Vitreous (glassy) to greasy
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Physical properties

Hardness: 7 on Mohs scale (cannot be scratched by steel). Color: White to off-white with yellowish-brown surface staining. Luster: Vitreous (glassy) to greasy. Crystal structure: Trigonal/Hexagonal, though rarely shows defined faces in tumbled or weathered specimens. Cleavage: Poor/None (conchoidal fracture). Specific Gravity: 2.65.

Formation & geological history

Quartz is formed in a wide variety of environments, most commonly via hydrothermal activity in veins or as a major constituent of igneous rocks like granite. The yellowish tint is a result of iron oxide (limonite or goethite) leaching into cracks or coating the surface over geological time.

Uses & applications

Used in industry for glassmaking and abrasives. High-purity quartz is used in electronics for its piezoelectric properties. In common forms like this, it is used for gravel, landscaping, or as a decorative 'pocket stone' for collectors.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. 'Milky' quartz gets its opacity from tiny fluid inclusions of gas or liquid trapped during crystal growth. It is highly resistant to chemical weathering.

Field identification & locations

Identify in the field by its hardness (will scratch glass easily) and lack of cleavage. This specific specimen looks like a river-worn or tumbled pebble. It is found globally, particularly in areas with metamorphic or igneous bedrock.

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