The best replacement for gypsum is lime.

The best alternatives to gypsum are rated as following:
★★★★★  lime
★★  drywall
★★  sheetrock
★★  plaster
★  anhydrite
★  calcite
★  limestone
★  dolomite
★  halite
★  nigari
★  calcium carbonate
  plaster of paris
  targhee
  perlite
  lime plaster
  calcium sulfate
  hardiflex
  selenite
  calcium sulphate
  pvc ceiling
  talc

Your alternative for gypsum is not listed? Suggest!
Speaking about gypsum, one probably shouldn't forget about clay soil.

Other search terms related to gypsum and their ratings are:
★★★★★ clay soil
★★★★ ast soil conditioner
★★ cement
You have in mind a companion for gypsum and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of gypsum in all years. Click on graph for more.
gypsum
lime
drywall