Cuttlefish Bone

Cuttlebone is the chalk-like, foamy, hard yet brittle internal structure of a cuttlefish. This gas-filled, chambered structure functions both as the cuttlefish's skeletal structure, and as a kind of rigid buoyancy aid. The cuttlebone is full of tiny holes, and the cuttlefish is essentially able to change the mix of liquid and gas in those holes to make itself more or less dense than seawater, allowing it easily to move up and down. This structure is what makes it distinctly different from a squid: squid have a flexible, feather-shaped structure inside their bodies, whereas cuttlefish have this broader and foamier internal 'shell' called the cuttlebone. Cuttlebone is an abundant material, and can often be found washed up along the shore in the UK. This calcium-rich material if a good source of nutrients for caged budgerigars and other pets. It is also commonly used by goldsmiths and jewellers as a mould for casting small metal objects. Its brittleness makes it easy to carve into with intricate detail, and it is naturally resistant to the heat of molten jewellery metals like silver and gold.