Related Clues:

• Pink pen has run out
• Material from reef originally surrounded by blackish rock
• My beer left unfinished — it's sort of pink
• Jewellery material: gracious lady's left half back
• What diamond is made of, said to be hard stuff
• Leader of Commons' test for marine growth
• Orangey-pink
• Losing a right to enclose sea-life
• Reef-forming sea life
• A number take exam, naturally it's hard
• She got top marks at the exam
• Scene of gold rush includes gold material for necklace
• Charlie said to be a pinkish colour
• Hard substance on the seabed
• Skeleton found in reef?