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 Chalk Uses. We have provided you with all information about Chalk rock here. Chalk is a soft, white, powdery limestone consisting mainly of fossil shells of foraminifers. Chalk is available in grey, white, yellow colors. The streak of a rock is the color of powder produced when it is dragged across an unweathered surface. The streak of Chalk is white. Get to know more about Chalk rock and characteristics of Chalk rock in the next sections.