metamorphic
Greenstone with Quartz Veining
Epidiorite or Metabasalt with SiO2 (Quartz) veins
Hardness: 6-7 (Mohs); Color: Dark green matrix with white/creamy veins; Luster: Dull to waxy on green parts, vitreous on white veins; Structure: Microcrystalline with fractured vein filling; Cleavage: None (conchoidal fracture).
- Hardness
- 6-7 (Mohs)
- Color
- Dark green matrix with white/creamy veins
- Luster
- Dull to waxy on green parts, vitreous on white veins
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Physical properties
Hardness: 6-7 (Mohs); Color: Dark green matrix with white/creamy veins; Luster: Dull to waxy on green parts, vitreous on white veins; Structure: Microcrystalline with fractured vein filling; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed through regional metamorphism of mafic igneous rocks (like basalt) at low-to-medium heat and pressure. White veins formed later as silica-rich hydrothermal fluids filled fractures. Common in Archean to Proterozoic greenstone belts.
Uses & applications
Primarily used as decorative stones, river rock landscaping, and occasionally lapidary art (cabs). Historically used for stone tools due to toughness.
Geological facts
Greenstone belts are some of the oldest geological formations on Earth, often containing vital mineral deposits like gold. The green color usually comes from minerals like chlorite, actinolite, or epidote.
Field identification & locations
Identify by its distinct olive-to-forest green color and hardness (cannot be scratched by a steel knife). Look for it in glacial till, riverbeds, and ancient volcanic terranes.
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