Millie Gunn, age 10, of Pierson, Iowa, for her question:

What is gypsum?

Sometimes a deposit of gypsum is spread on the surface of the land. Chances are you would mistake it for a stretch of fine, white sand. The famous White Sands Desert of New Mexico is actually made of Gypsum crystals. Gypsum is also the mineral used to make plaster of Paris. In nature, it is a white mineral so soft that you can scratch a line on it with your fingernail.

The mineral gypsum is a chemical compound of calcium and sulphur blended with generous amounts of water. In marry places deposits Were made when the Water Evaporated from ancient seas and left the salty chemicals behind. Gypsum in the ground tonds to make our water hard, and mined gypsum is Used to add limy fertilizer to the soil.