metamorphic
Eclogite
Eclogite (Omphacite-Garnet Metamophic Rock)
Hardness: 6-7 (Mohs scale); Color: Grass-green (omphacite) with red to pink dots (almandine-pyrope garnet); Luster: Vitreous to dull; Crystal structure: Granular; Specific Gravity: 3.2-3.6.
- Hardness
- 6-7 (Mohs scale)
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Grass-green (omphacite) with red to pink dots (almandine-pyrope garnet); Luster: Vitreous to dull; Crystal structure: Granular; Specific Gravity: 3.2-3.6.
Formation & geological history
Formed at extremely high pressures and temperatures (typically >45km deep) in subduction zones or where continental plates collide. This represents the metamorphism of basaltic crust into high-density rock during oceanic subduction.
Uses & applications
Primarily of interest to geologists and collectors. Due to its density and hardness, it was historically used for making polished stone tools like axe heads in Neolithic Europe.
Geological facts
Eclogite is often called the 'Christmas Tree Rock' because of its vibrant green and red coloration. It provides critical evidence to scientists about the processes occurring in the Earth's upper mantle and deep crust.
Field identification & locations
Identify by the distinct 'red on green' appearance (garnets in an omphacite matrix). Commonly found in the Alps, Norway, and the Aegean islands of Greece. Its presence often indicates a former subduction zone.
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