Gypsic horizon
These horizons contain more than 20% of visible gypsum that is apparently of pedogenic origin, with a minimum thickness of 0.1 m. Gypsum is visible in the soil as clusters of platy shaped crystals. It is soft and can be crushed with a thumb nail. Gypsum is readily distinguished from calcareous accumulations, and do not fizz when mixed with 0.1N HCl.
It is commonly found in clay subsoils below calcareous horizons in arid and semiarid climates. Gypsum can also be found as evaporites on and in inland saline lakes (playas) and coastal salinas.
Gypsum crystals
Photo credit: Andrew Biggs