metamorphic
Greenstone / Metabasalt
Chlorite schist or Epidiorite
Hardness: 6-7 (Mohs scale), Color: dull green to grayish-green, Luster: dull to vitreous, Structure: fine-grained/aphanitic with some foliation, Specific Gravity: approx 2.85-3.0.
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Physical properties
Hardness: 6-7 (Mohs scale), Color: dull green to grayish-green, Luster: dull to vitreous, Structure: fine-grained/aphanitic with some foliation, Specific Gravity: approx 2.85-3.0.
Formation & geological history
Formed through the low-grade metamorphism (greenschist facies) of mafic igneous rocks like basalt. This process often occurs in mountain-building zones or oceanic crust subduction.
Uses & applications
Historically used for making ground stone tools (axes/adzes); currently used as crushed stone for road construction, garden landscaping, and architectural veneers.
Geological facts
The green color is primarily due to the presence of chlorite, epidote, or actinolite minerals that replace the original dark minerals in the basalt.
Field identification & locations
Identify in the field by its characteristic 'pistachio' or 'moss' green dull hue, lack of visible crystals without a lens, and superior hardness compared to shale.
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