This is such a great way to make your own unique jewelries. The ending effects are just amazing. Also it does not cost you much to make these wonderful necklaces, earrings, or other accessories.
Get some clear marbles and work from there. Heat them up in your oven and pour them into freezing cold water. Watch them turn into cracked marbles magically in front of you. The temperature and time may varies depending on your oven and the size of your marbles, etc. You can try a few marbles if you are not sure.
Doesn’t it sound like a great science project for kids? (Be careful of the hot surfaces though!)