True about x-ray diffraction data for set gypsum products:
The setting reaction takes time to complete and changes in the mixture begin as soon as the hemihydrate and water are mixed together.  X-ray diffraction data for set gypsum products indicate that there is less than 50% dihydrate present in Type IV and V stones, about 60% in Type II die materials, and over 90% in Type I plasters.
Phillips Science of Dental Materials ed 12 pg 184
There is less than 50% dihydrate present in type 4 stones
There is less than 40% dihydrate present in type 2 die materials
There is less than 30% dihydrate present in type 1 plaster
There is less than 20% dihydrate present in type 5 stones