a beautiful gypsum crystal no matrix in perky box tagged this is from and old stock collection from 1960s Gypsum blooms, also known as "green tides", are a common occurrence in the Salton Sea. These blooms are caused by the precipitation of gypsum, which is the most common sulfate mineral on Earth. Gypsum blooms can occur when there are increases in calcium and sulfate ion concentrations, or when temperatures fluctuate. The Salton Sea is a salty lake and California's largest inland body of water. The sea has been receding due to low water input, which has increased the concentration of ions in the water and led to gypsum precipitation