Re: Why there is calcium carbonate in the chalk?

There are three reasons for the inclusion of calcium carbonate: opacity, color and volume. In addition, this mineral is inexpensive and abundant. Since there are still a great deal of black boards and other dark surfaces to color, the most contrasting color to black is white. Calcium carbonate is a natural white pigment that possesses high "hiding power" (very opaque and covers over surfaces well). Finally, since it is a solid, it provides a lot of bulk (thickness or volume) to paints and is a great tint base...