Related Clues:

• Precious thing
• Stone made of hydrated silica
• Tourmaline or amethyst, e.g.
• A birthstone
• It's a form of hydrated silica
• Amethyst, e.g.
• Tourmaline, e.g.
• Garnet or topaz
• 55th-anniversary gift
• Outback gem
• Stone for many a Libra
• Diamond or emerald
• Ruby or garnet
• Play-of-color gem
• Libran birthstone