Eclogite (Garnet-Omphacite)
“The densest rock at Earth's surface”
Eclogite is a spectacular high-pressure metamorphic rock made of vivid green omphacite pyroxene and deep red garnet. It forms at extreme depths in subduction zones — typically 45-100 km down — and its high density may play a key role in driving the sinking of tectonic plates.
omphacite, garnet (pyrope-almandine), rutile, kyanite, coesite (rare), diamond (rare)
Western Norway, Dabie-Sulu (China), Zermatt-Saas (Switzerland), Cabo Ortegal (Spain), Kokchetav (Kazakhstan)
6-7
Some eclogites contain microdiamonds formed at depths exceeding 120 km — proving that these rocks once traveled to extraordinary depths before being returned to the surface.
Test Your Knowledge
Why is eclogite's extreme density significant for plate tectonics?
Photo Attribution
Title: Eclogite (Late Silurian to Early Devonian, ~400-423 Ma; Almenningen, Vestland, Norway) 19.jpg
Author: James St. John
License: CC BY 2.0
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