Jewel & Gem Goop

From The Ultimate Book of Kid Concoctions

1/2 c white glue
2 c rock salt
6-8 drops food coloring

1. Mix rock salt and food coloring together. Add glue and continue mixing for 2-3 minutes.
2. Mold and sculpt Jewel & Gem Goop, using your hands.
3. Place Jewel & Gem sculptures on a piece of cardboard to dry. Drying time will vary depending on size and thickness of your creation.

I haven't made this yet, but I found this blog where someone else has.