Mineral on Igneous Rock
Quartz Druzy on Basalt
Silicon Dioxide (SiO2) on Mafic Volcanic Rock
Hardness: 7 (Quartz) / 5.5-6 (Basalt). Color: Clear/white crystals on dark grey/black matrix. Luster: Vitreous (Quartz) to Dull (Basalt). Crystal Structure: Hexagonal/Trigonal. Cleavage: None (Conchoidal fracture). Specific Gravity: 2.65.
- Hardness
- 7 (Quartz) / 5
- Color
- Clear/white crystals on dark grey/black matrix
- Luster
- Vitreous (Quartz) to Dull (Basalt)
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Physical properties
Hardness: 7 (Quartz) / 5.5-6 (Basalt). Color: Clear/white crystals on dark grey/black matrix. Luster: Vitreous (Quartz) to Dull (Basalt). Crystal Structure: Hexagonal/Trigonal. Cleavage: None (Conchoidal fracture). Specific Gravity: 2.65.
Formation & geological history
Formed through hydrothermal activity where silica-rich fluids circulated through cavities (vesicles) or cracks in cooling basaltic lava flows. This specimen features a 'druzy' coating, where tiny crystals form on a rock surface or within a geode shell.
Uses & applications
Used primarily as decorative collector specimens, in ornamental jewelry as 'druzy quartz', and occasionally in metaphysical collections.
Geological facts
Quartz druzy occurs when groundwater carrying dissolved silica precipitates crystals inside pockets created by trapped gas or seismic fracturing in volcanic rock. Basalt is the most common volcanic rock on Earth and even makes up much of the ocean floor and the lunar maria.
Field identification & locations
Identify in the field by looking for sparky, crystalline crusts inside dark, heavy volcanic rocks. It is commonly found in volcanic regions such as the Deccan Traps in India, the basalt flows of the Pacific Northwest, and various regions in Brazil.
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