Rocks are naturally occurring solids which are composed of minerals & have been used by humans since ages. From Stone Age, rocks are used for various purposes. Also, the metals and minerals found in rock play an important role in our life. Get to know all the Diorite Uses. We have provided you with all information about Diorite rock here. Diorite is a grey to dark-grey intermediate intrusive igneous rock composed principally of plagioclase feldspar,biotite, hornblende, and pyroxene. Diorite is available in black, brown, light to dark grey, white colors. The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Diorite is bluish black. Get to know more about Diorite rock and characteristics of Diorite rock in the next sections.