Omphacite, Almandine (Dimensions: 4" x 2.5" x 1.5") ::Locality: Nordfjord, Sogn og Fjordane, Norway ::Description: Chunk of eclogite consisting of green omphacite and red almindine garnet. Eclogite forms during subduction (over 35km deep) under high pressure in the mantle (lowest part of Earth's crust) and thus useful for studying plate tectonics.