metamorphic
Eclogite
Eclogite (High-pressure metamorphic rock)
Hardness: 6.5-7.5 (due to garnet and pyroxene); Color: distinctly red (garnet) and green (omphacite pyroxene), though can appear dark when unpolished; Luster: Vitreous to dull; Crystal structure: Coarse-grained granular; Specific gravity: Very high (3.2-3.6).
- Hardness
- 6
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7.5 (due to garnet and pyroxene); Color: distinctly red (garnet) and green (omphacite pyroxene), though can appear dark when unpolished; Luster: Vitreous to dull; Crystal structure: Coarse-grained granular; Specific gravity: Very high (3.2-3.6).
Formation & geological history
Formed under conditions of extremely high pressure and relatively high temperature in the Earth's mantle or deep crust during subduction. It represents the highest grade of regional metamorphism and is often associated with ancient mountain-building events.
Uses & applications
Primarily of interest to researchers for understanding mantle processes and subduction zones; occasionally used as a decorative stone or for heavy-duty construction aggregate due to its extreme density and hardness.
Geological facts
Eclogite is often called the 'Christmas Tree Rock' because of its bright green and red coloration when polished. It is sometimes the host rock for diamonds in kimberlite pipes.
Field identification & locations
Look for a heavy, dense rock with visible red garnets embedded in a dark green or black matrix. It is found in high-pressure metamorphic belts like the Alps, Norway, or the Franciscan Complex in California. For collectors, look for distinct, non-fractured garnets.
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