anorthosite
Anorthosite - leucocrat igneous or coarse igneous rock, black, gray, brown or greenish gray, consisting of almost plagioclase alone. They account for more than 90% of the volume of anorexia. Small amounts of pyroxenes may occur. The content of anthracite in plagioclase can range from 20 to 100%. Labortor anthraces are called labradorites. It is estimated that terrestrial anortoses were formed at a depth of 15-20 km. Hunt named the "anortosite" to emphasize that the building plagioclase does not have monoclinic but triangular symmetry.