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 Rhyodacite Uses. We have provided you with all information about Rhyodacite rock here. Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. Rhyodacite is available in black to grey, dark greenish - grey colors. The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Rhyodacite is black. Get to know more about Rhyodacite rock and characteristics of Rhyodacite rock in the next sections.