mineral
Milky Quartz (Ferruginous)
Silicon Dioxide (SiO2)
Hardness: 7 (Mohs); Color: White to tan/yellowish (due to iron oxidation); Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 (Mohs)
- Color
- White to tan/yellowish (due to iron oxidation)
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 (Mohs); Color: White to tan/yellowish (due to iron oxidation); Luster: Vitreous to greasy; Crystal Structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed in hydrothermal veins, pegmatites, and igneous rocks. This specimen likely weathered out of a quartz vein and has acquired a yellow-brown surface stain from iron oxides (ferruginous quartz).
Uses & applications
Used primarily in industrial glass making, electronics, and as an abrasive. Specimens like this are common in landscaping and basic mineral collections.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. Its 'milky' appearance is caused by tiny fluid inclusions of gas and/or liquid trapped during crystal growth.
Field identification & locations
Identify by its hardness (it will scratch glass) and lack of cleavage. Commonly found in riverbeds, mountain ranges, and gravel pits worldwide.
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