Related Clues:

• It's less dense than quartz
• Key composition?
• Color of unbleached linen
• Tusk material
• Neutral tone
• Suede shade
• Iridescent mineral
• Off-white
• Certain birthstone
• Birthstone for 31-Across
• Gem with a play of colors
• Raw silk color
• Down Under gemstone
• Word with tower or coast
• Raw linen color