Eclogite

Description

Sample of eclogite (https://en.wikipedia.org/wiki/Eclogite) from southern Greenland collected by the late Dr. Helen Lang (WVU). Eclogite is typically composed of a red garnet (usually almandine or pyrope; https://en.wikipedia.org/wiki/Garnet) and green omphacite (a sodium-rich pyroxene; https://en.wikipedia.org/wiki/Omphacite), often with other high pressure minerals like kyanite. Eclogites form from deep-subduction and high pressure / low temperature metamorphism of mafic ocean crust in subduction zones. Eclogites are unusual for crustal rocks because they are denser than the surrounding mantle rocks, and it it the mass of eclogite that helps to drag a plate down.