The late 80's brought to the New Age community a very interesting toy, the instrument with angelic tone - crystal singing bowl.
The crystal alchemy sets are very popular these days and are a really good sounding instrument. These bowls are made of melted quartz family minerals such as crystal, citrine, amethyst or partials of other semiprecious minerals. The quartz is heated to 4000 degrees Celsius and formed in the shape of bowl. Some of crystal bowls also come plated with gold or platinum (I have to make a disclaimer here, I haven't seen any laboratory results of testing the material).
Yes indeed, crystal singing bowls sound nice, but no matter how you play these bowls they will never give you as wide a variety of overtones as the polyphonic sound of bronze made singing bowls. I always compare the sound of crystal singing bowls to the sound of wine glasses even though the tones of the alchemy sets are pleasing to the ear.Many people address the mystical properties of the mineral kingdom to the singing bowls made of quartz. I'll leave it to you to make your own judgments about this.