Gypsum karst is very rare. It depends on deposits of gypsum or anhydrite, often also called alabaster. Chemically it is calcium sulfate CaSO4.
Gypsum is much rarer than limestone, as it needs very special conditions:
Now you have gypsum, but there is another problem: water is able to solute gypsum without the complicated CO2 stuff with limestone. And it will do it much faster and be able to solute a much higher amount!
For gypsum karst this means:
The longest gypsum cave of the world is Optimisticheskaya Cave in Ukraine with 165 km of passage. Because of their size, numerous gypsum caves are used as show caves.