English: Kyanitic eclogite from Turkey.

Eclogite is an attractive, scarce, crystalline-textured, very high-grade metamorphic rock. It is dominated by red garnet (pyrope or almandine) and green omphacite pyroxene. Eclogite appears to be moderately common in portions of the upper mantle, but occurs in few places at the Earth’s surface. Eclogites have the same chemistry as basalts and gabbros (= oceanic crustal rocks), but have different mineralogies. Eclogites form by very high grade metamorphism of oceanic crust at mantle depths along subduction zones. Uplift of eclogites back to the surface often involves some retrograde metamorphism and the formation of new minerals, resulting in retrograde eclogites.

The eclogite seen here is from eastern Turkey. The dark green is omphacite pyroxene, the slightly reddish gray is garnet, and the whitish-grayish is quartz. The sparsely-scattered, blue-colored crystals are kyanite, an aluminum silicate mineral - Al2SiO5. (See: www.flickr.com/photos/jsjgeology/albums/72157677871157642) Click on the photo to zoom in and look around for the kyanite.

Locality: unrecorded / undisclosed site attributed to the Arguvan District, Malatya Province, eastern Turkey