metamorphic
Milky Quartz Vein in Mafic Rock
Quartzite vein in Metabasalt (SiO2 base)
Hardness: 7 (Quartz portion), 5-6 (Basalt portion). Color: Opaque white to tan (quartz) and dark grey (host rock). Luster: Vitreous to greasy. Crystal structure: Trigonal/Hexagonal. Cleavage: Indistinct. Specific gravity: ~2.65.
- Hardness
- 7 (Quartz portion), 5-6 (Basalt portion)
- Color
- Opaque white to tan (quartz) and dark grey (host rock)
- Luster
- Vitreous to greasy
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Physical properties
Hardness: 7 (Quartz portion), 5-6 (Basalt portion). Color: Opaque white to tan (quartz) and dark grey (host rock). Luster: Vitreous to greasy. Crystal structure: Trigonal/Hexagonal. Cleavage: Indistinct. Specific gravity: ~2.65.
Formation & geological history
Formed via hydrothermal activity where mineral-rich hot water filled cracks in cooling volcanic rock (basalt or diabase). Over millions of years, the water evaporated or cooled, leaving behind concentrated silica that crystallized. The rounded shape indicates recent erosion in a high-energy environment like a river or beach.
Uses & applications
Primarily used as decorative landscaping stone or for educational collecting. Quartz itself is used in electronics and glass-making, while basaltic rock is used as industrial aggregate.
Geological facts
Quartz is the second most abundant mineral in Earth's continental crust. This specific specimen is an excellent example of 'vein Filling,' a process often associated with the deposition of gold and other precious metals in metamorphic terrains.
Field identification & locations
Identify in the field by looking for white stripes or blobs cutting through darker, finer-grained stones. The quartz will scratch glass, whereas the darker host rock may not as easily. Common in glacial tills and riverbeds throughout North America and Europe.
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