You will need:
powdered alum, available in the spice section of the supermarket
water
a small pan
a wooden spoon
food coloring (for amounts, see below)
several small jars
paper towels
1. Measure 4 teaspoons of water and 3 teaspoons of alum into the pan.
2. Add drops of food coloring to achieve the desired color (see the color list below for ideas).
3. Bring the mixture to a complete boil, stirring for a few seconds until all of the alum is dissolved.
4. Allow the mixture to cool two minutes. Carefully pour the alum solution into the jar, and let it sit uncovered and undisturbed for three days. Soon you will begin to see crystals forming at the bottom of the jar.
Do not move the jar
5. After three days, carefully pour off the excess water and gently remove the crystals. Spread them evenly on a paper towel to dry.
Color Chart:
"
emeralds" 10 drops green
"
rubies" 12 drops red
"
diamonds" no color
"
topaz" 10 drops yellow
"
sapphires" 10 drops blue
"
amber" 6 drops yellow + 2 drops red + 1 drop green
(
http://www.nationalgeographic.com/)