How to Make Bismuth Crystals

Bismuth, element number 83 on the periodic table of elements, grows as square, iridescent crystals with smooth outside edges and a stair-step pattern on the inner edge. Crystals grown this way are called hopper crystals. Their iridescent color pattern forms from an oxide layer on the outside of the crystals. While bismuth crystals are rare in nature, you can make large, intricate bismuth crystals at home in your kitchen.

Break up the raw bismuth into nickel-sized pieces by placing the bismuth inside an old towel and hitting it with short, controlled blows with a rubber mallet. Place them into a small but deep stainless steel sauce pan. Cover the bottom of the pan in bismuth pieces, then layer another layer on top of that.

From: http://www.mining-mining.com/products/High-purity-bismuth/