Section 14537 Of Article 2. Definitions From California Food And Agricultural Code >> Division 7. >> Chapter 5. >> Article 2.

. (a) "Gypsum" means calcium sulfate dihydrate, a mineral used in the fertilizer industry as a source of calcium and sulfur which is also known as landplaster.
  (b) "Phosphatic sulfate gypsum" means a by-product of calcium dihydrate from the manufacture of phosphoric acid, also known as phosphogypsum.