metamorphic
Green Slate (Greenstone)
Foliated Metamorphic Rock (rich in Chlorite/Epidote)
Hardness: 2.5-4 Mohs (soft); Color: Dull grayish-green; Luster: Matte to earthy; Structure: Fine-grained, foliated with slight slaty cleavage; SG: 2.7-2.9
- Hardness
- 2
- Color
- Dull grayish-green
- Luster
- Matte to earthy
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Physical properties
Hardness: 2.5-4 Mohs (soft); Color: Dull grayish-green; Luster: Matte to earthy; Structure: Fine-grained, foliated with slight slaty cleavage; SG: 2.7-2.9
Formation & geological history
Formed through low-grade regional metamorphism of clay-rich sedimentary rocks (like shale) or volcanic ash. The green color is primarily due to the presence of chlorite minerals formed under high pressure and low temperature conditions.
Uses & applications
Used for roofing tiles, billiard tables, flooring, and decorative garden stones. Larger specimens are popular for engraving and carvings due to their softness.
Geological facts
Green slate is a common variety of slate that gets its distinctive hue from iron-magnesium silicates. It has been used for centuries as a durable building material in the British Isles and the Northeastern United States.
Field identification & locations
Identify by its dull green color, fine-grained texture, and tendency to split into thin sheets. Commonly found in riverbeds or coastal areas near former mountain-forming regions (orogenic belts).
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