metamorphic
Eclogite (retrograded)
Eclogite (Omphacite-Garnet rock)
Hardness: 6-7.5. Color: Mottled green (omphacite pyroxene) with reddish-brown spots (almandine-pyrope garnet). Luster: Dull to vitreous. Structure: Granular, heavy (high specific gravity).
- Hardness
- 6-7
- Luster
- Dull to vitreous
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Physical properties
Hardness: 6-7.5. Color: Mottled green (omphacite pyroxene) with reddish-brown spots (almandine-pyrope garnet). Luster: Dull to vitreous. Structure: Granular, heavy (high specific gravity).
Formation & geological history
Forms under extremely high pressure and moderate-to-high temperature conditions typical of deep subduction zones (mantle depths). This specimen shows signs of retrograded metamorphism, where it has weathered during its journey back to the surface.
Uses & applications
Primarily of interest to researchers for studying plate tectonics and mantle processes; occasionally used as a decorative stone or abrasive.
Geological facts
Eclogite is often called the 'Christmas Tree Rock' due to its classic green and red coloration. It is one of the densest silicate rocks found on the Earth's surface.
Field identification & locations
Look for a very heavy, dense rock with a distinctive mix of green minerals and red/brown circular crystals. Commonly found in areas of exhumed deep crust like the Alps, Norway, or the Franciscan Complex in California.
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