£3.50 – £14.00
Eclogite is an uncommon metamorphic rock, composed of mainly two minerals, reddish-brown garnets and omphacite, a green pyroxene. Other minerals, such as blue kyanite and white quartz may also be present. Over all, it is an attractive looking yet rare rock, with a vibrant green colouration with red garnets to break it up. These rocks come from Almenning, Norway. Specimens are supplied in card trays with labels and come available in 4 sizes.
Eclogite is an uncommon metamorphic rock. It typically forms from the high pressure metamorphism of mafic igneous rock such as basalt and gabbros at depths of 50km or more in the mantle or lower crust. It is composed of mainly two minerals, reddish-brown almandine or pyrope garnet crystals and the green sodium rich pyroxene omphacite. Other minerals, such as blue kyanite and white quartz may also be present. Isotope dating of the Norwegian eclogites in the 1970's and 1980's indicates they are early Palaeozoic (450-400 million years old) in age and this suggests they formed during the Caledonian orogeny, which formed the majority of the mountains in northern Britain and Scandnavia.
Studies have shown that western Norway had been dragged down to great depths beneath a thick pile of nappes that was building up as the mountain chain formed. The discovery, about ten years ago, of micro-diamonds in eclogites was remarkable and further proved high pressure and depths at which the rocks formed. They are too small to be seen with the naked eye, however, don't expect one in your sample. These examples come from Almenning, Norway and are available in various sizes and come supplied in a card tray with a label.