Possible Clues:

• ___-i-noor diamond
• --- -i-noor diamond
• -- -i-noor diamond
• -- -i-noor (big diamond)
• __-i-noor diamond
• Soapmaking compound, chemically
• Potassium hydroxide, to chemists
• The ___-i-Noor Diamond
• __-i-noor: 106-carat diamond
• -- -i-noor (famous diamond)