Metamorphic or Igneous with Mineral Inclusion
Quartz Vein in Gneiss or Basalt
Milky Quartz (SiO2) within Metamorphic Host Rock
Hardness: 7 (Quartz) / 5-6 (Matrix). Color: White milky veins with dark grey/black host rock. Luster: Vitreous to waxy. Structure: Massive/Microcrystalline. Specific Gravity: ~2.65.
- Hardness
- 7 (Quartz) / 5-6 (Matrix)
- Color
- White milky veins with dark grey/black host rock
- Luster
- Vitreous to waxy
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Physical properties
Hardness: 7 (Quartz) / 5-6 (Matrix). Color: White milky veins with dark grey/black host rock. Luster: Vitreous to waxy. Structure: Massive/Microcrystalline. Specific Gravity: ~2.65.
Formation & geological history
Formed through hydrothermal processes where silica-rich fluids filled fractures in existing rock at high pressure. This usually occurs deep in the Earth's crust during mountain-building events (Orogeny).
Uses & applications
Commonly used as construction aggregate, road stone, or as decorative beach pebbles for landscaping and coastal protection.
Geological facts
These are often called 'Wishing Stones' by beachcombers if the white band forms a complete unbroken circle around the rock. The high hardness of the quartz makes it more resistant to erosion than the surrounding dark rock.
Field identification & locations
Identify in the field by the distinct color contrast and the fact that the white quartz will scratch glass while the darker matrix might not. Found globally on rocky beaches and riverbeds.
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