Source: Martha Stewart
You'll need an assortment of glass and pottery shards to make this necklace.
Fill a plastic container with a small amount of water, and set a shard of sea glass inside; it should be slightly covered but not submerged (drilling the shard in water will guard against cracking and prevent it from getting too hot).
Wearing safety glasses and holding the shard with the eraser end of a pencil, make a hole in glass using a craft drill, below right, fitted with a No. 61 diamond bit (it may take a few tries to drill through completely).
Cut a length of silk cord long enough to fit over your head when looped. String a shard onto the cord, and tie with a double knot. Continue adding shards at even intervals. When finished, tie the cord ends together with a double knot.