Grain diorite. Polarised light micrograph of a sample of grain diorite in thin section. Diorite is an intrusive igneous rock, found on the margins of granite batholiths. It contains plagioclase anorthite (less than 50%, by definition) and hornblende, often with accessory inclusions of magnetite, ilmenite or quartz. The colour is an overall dark grey, with a medium to coarse grain. Its main use is as a building stone. Magnification x6 at 6x7cm size. Magnification: x11 at 5x4 inch size.
