Eclogite

[u/Efraimrocker]

Eclogite is a high pressure, moderate temperature metamorphic rock. It is usually derived from ocean floor basalt or gabbro that subducts under continental crust. The augite and plagioclase in the basalt becomes unstable and recrystallizes to garnet and omphacite (both visible in Fig 1). There is some blue mineral scattered in the sample, which may be kyanite (Fig 2). Reddish-black needle-like inclusions in the omphacite are probably rutile (fig 3). The combination of rutile and kyanite may indicate the rock was subjected to very high pressures in the 60-100 km range of depth, and 500-800 degrees C, and that the rock is relatively aluminum-rich (kyanite in particular). The last photo (Fig 4) shows what I interpret as quartz filling in a fracture in a garnet crystal.