Related Clues:

• Glassmaking ingredient
• Quartz material
• Glass ingredient
• Opal, essentially
• Sand or quartz
• Glass component
• Sand, basically
• Flint is a form of it
• It's in the sand
• Quartz or opal
• Glassmaker's material
• Cement ingredient
• Glass base
• Quartz, for example
• Ingredient in ceramics