One can find a number of castable gemstones in catalogs from Rio
Grande or other fine gemstone dealers.
Keep in mind that gemstones need to be of good quality even
sapphires and ruby’s (i.e. corundum)!
I’ve seen sapphires color shifting just by resoldering prongtips
turning from fine blue into dark blue.
They do get darker from prelonged heating.
Another aspect which need to be considered is the price of the
gemstone after heat treatment process.
For the little ones amongst them it doesn’t matter thatmuch. The
bigger ones however will reach lower prices and fetch lower quality
by heat treatment.
One can tell if (for example blue sapphires) are heat treated or not
by inspecting the spectrum lines.
I’m not a specialist in this matter but I do know about the missing
spectrum lines in heat treated sapphires.
Tanzanite is another good example of heat treated gemstone but this
treatment causes a much better price as the original gemstone.
Let the cast items cool slowly without quenching them to fast
causing damages of
Be aware of these facts and take them in account of possible
Have fun and enjoy