Related Clues:

• Semiprecious gem
• Form of silicon dioxide
• Something precious
• Oyster product
• It's softer than quartz
• A gem of a name?
• Birthstone of some Libras
• 16-Down's birthstone
• Birthstone before topaz
• Stone
• Super Trouper Bert
• October's gemstone
• Silica mineral
• Fire __
• Oyster prize