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 Diabase Uses. We have provided you with all information about Diabase rock here. Diabase is a fine-grained igneous rock which is composed mostly of pyroxene and feldspar. Diabase is available in dark grey to black colors. The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Diabase is black. Get to know more about Diabase rock and characteristics of Diabase rock in the next sections.