igneous
Quartz Veined Diorite or Basalt
Crystalline Silicon Dioxide (Quartz) in Mafic Igneous Host (Basalt/Diorite)
Hardness: 6-7 (Mohs); Color: Dark grey with white vein; Luster: Dull to Vitreous; Crystal Structure: Cryptocrystalline to fine-grained; Specific Gravity: 2.7-3.0
- Hardness
- 6-7 (Mohs)
- Color
- Dark grey with white vein
- Luster
- Dull to Vitreous
Identified More igneous →
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark grey with white vein; Luster: Dull to Vitreous; Crystal Structure: Cryptocrystalline to fine-grained; Specific Gravity: 2.7-3.0
Formation & geological history
Formed via intrusive or extrusive volcanic processes. The white portion is a hydrothermal quartz vein that filled a fracture in the darker host rock during later cooling stages.
Uses & applications
Commonly used as aggregate for road construction, landscaping, and as a decorative river stone.
Geological facts
The sharp contrast in color is due to 'fractional crystallization' where different minerals solidify at different temperatures and pressures within the Earth's crust.
Field identification & locations
Identify in the field by the distinct color boundary and 'scratch test' (quartz will scratch glass). Commonly found in riverbeds, glacial tills, and volcanic terrain.
