Related Clues:

• Santa ___
• Crystalline mineral
• Vermiculite, essentially
• Isinglass
• Some sheets
• Brass-yellow minerals
• Popular insulator
• Flaky rock
• Flaky mineral
• Muscovite, e.g.
• Scaly mineral
• Insulation material
• Mineral used for insulation
• Constituent of biotite
• It comes in sheets