Eclogite

Physical Properties

Hardness: 6-7.5 (Mohs scale), Color: Pinkish-red (garnet) and Green (omphacite), Luster: Vitreous to dull, Crystal structure: Granular/crystalline, Cleavage: Poor, Specific Gravity: 3.2-3.6

Formation & Geological History

Formed under high-pressure, low-to-moderate temperature conditions (high-pressure metamorphism) in subduction zones within the Earth's mantle or deep crust. It represents the conversion of basaltic crust at depths typically exceeding 45-60 km.

Uses & Applications

Primarily of interest to geologists and collectors for research into tectonic processes; occasionally used as a decorative stone or minor gemstone source if garnets are of high quality.

Geological Facts

Eclogite is often called the 'Christmas Rock' because of its festive red and green coloration. It is one of the densest silicate rocks and provides critical evidence for the recycling of the Earth's crust into the mantle.

Field Identification & Locations

Identify by the distinct association of red-to-pink garnets embedded in a green pyroxene (omphacite) matrix. Found in 'blueschist' terranes, subduction complexes, or as xenoliths in kimberlite pipes. Common in areas like the Franciscan Complex in California or the Alps.

Identified on: 5/1/2026

Mode: Standard