Certified GKH Gardening Expert
It is used to add calcium and magnesium to the soil and gypsum is a common substitute.
To the best of my knowledge dolomite & or perlite are soil additives to keep your soil loose. Personally I don't like it in my soil mixes. You could use plain old playground or beach sand as an alternative. My beds are a mix of black dirt, peatmoss & sand. Peat moss will also keep your soil loose.
Hope this helps!