metamorphic
Eclogite
Eclogite (Omphacite-Garnet rock)
Hardness: 6.5-7.5 (Garnet) and 5-6 (Omphacite). Color: Typically distinctive red garnets set in a green pyroxene (omphacite) matrix, though this weathered specimen shows dark red garnets in a light grey-green weathered matrix. Luster: Vitreous to dull. Structure: Coarse-grained, non-foliated.
- Hardness
- 6
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7.5 (Garnet) and 5-6 (Omphacite). Color: Typically distinctive red garnets set in a green pyroxene (omphacite) matrix, though this weathered specimen shows dark red garnets in a light grey-green weathered matrix. Luster: Vitreous to dull. Structure: Coarse-grained, non-foliated.
Formation & geological history
Formed under extremely high pressures and relatively high temperatures in the upper mantle or lower crust, typically at depths of 50 km or more within subduction zones. It transitions from basaltic or gabbroic precursors.
Uses & applications
Primarily of scientific interest for studying mantle dynamics and plate tectonics; occasionally used as a decorative stone or for heavy-duty industrial abrasives due to high garnet content.
Geological facts
Eclogite is often called the 'Christmas Tree Rock' because of its classic red garnet and green omphacite coloring. It is a key indicator of high-pressure metamorphic facies.
Field identification & locations
Identify by looking for deep red, rounded garnets embedded in a dense, green or greyish-green silicate matrix. Commonly found in alpine or convergent boundary orogenic belts like Norway, the Alps, or the California Coast Ranges.
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