Growing your own "synthetic gemstones".
Materials
200 grams (7 oz) alum powder (available in a local pharmacy)
200 grams table salt
200 grams Epsom salt (available in a local pharmacy)
3 pieces of string, each about 15 cm (6") long
3 paper clips or washers
3 sheets of aluminum foil, approximately 30 cm (12") square
3 large plastic cups, at least 12 oz each
Hot tap water
3 plastic teaspoons
Roll of masking tape
Marking pen
Pocket magnifier
1. Fill each plastic cup about half full of hot tap water. In the first cup, begin stirring in spoonfuls of table salt until you can dissolve no more (usually about 68 spoons). Use a piece of masking tape and the marking pen to label this first cup NaCl. With a clean spoon repeat the procedure with the second cup, only this time use the Epsom salt. Label this cup MgSO4. In the third cup, stir in the alum powder and label it KAl(SO4)2.
2. Tie a paper clip on the end of each string. Wet one string with water and rub some salt crystals on it. Take a piece of aluminum foil and poke a small hole in the middle of it. Thread the free end of the salted string through the hole in the foil, and then cover the cup marked NaCl with the foil. Pull up on the string so that the paper clip is just touching the bottom of the cup and then secure the free end of the string to the top of the cup with a piece of tape.
3. Repeat step 2 first with the Epsom salt and then the alum powder. When all three solutions have been set up, place them in a safe location away from any direct heat or sunlight. In about one week, visible crystals should start to develop on the end of each string.
4. Using a magnifier, observe each crystal and draw a picture of its habit (shape). Compare the crystals you are growing to the three materials you started with and record your observations.
5. Allow the crystals to grow for another two to three weeks and use a millimeter ruler to keep track of their growth rate. Make sure that you note any changes in their appearance over time.
http://ericir.syr.edu/Projects/Newton/newtonalpha.html