Related Clues:

• Crystalline mineral
• Heat-resistant glass
• Crystal
• Hard rock
• Glass ingredient
• Glass component
• Proctor-___ (small appliance maker)
• Mineral
• Proctor's partner
• Silicon dioxide
• Amethyst, e.g.
• 7 on the Mohs scale
• Another name for flint
• Hard mineral
• Amethyst or jasper