Possible Clues:

• Can get up about what's pearly
• Necklace decoration
• Plenty of space at the north in the oyster
• Valuable material smashed by crane
• Decorative inlay material made of abalone
• Mrs Buck's mother?
• Shiny shell material
• Smooth material from northern bit of territory?
• Hard substance containing nitrogen on part of the estate?
• If it's up to 'er, can Pearl have an 18 down?