SHELL

Shell made of calcium carbonate, shells show a wide range of sizes and colours, from the iridescent colours of pearl oyster shells (Pinctada maxima and Pinctada margaritifera), blue-green iridescence of abalone, paua (the type of abalone that is found in the waters around New Zealand) and topshells (trochidae), to the delicate white and pink layers of the conch shell.

In addition to marine shells, a wide range of river and terrestrial shells is also used as beads and in jewellery, particularly if they show a colourful iridescence.

Occurrence

Shells are found worldwide. Conch is found in the Bahamas (where conch fritters are a favourite food), Madagascar and the Maldive Islands. Abalone molluscs are found off the coast of South Africa and the USA.

Maori people have a long tradition of gathering paua for its meat, as well as using the shell in their carvings and as a Taonga (the Maori word for treasure). Paua has become the shell associated with gifts from New Zealand.

Mother-of-pearl cabochons, mosaic pieces for inlay, or as decorative pieces. Some shells have an iridescent coating of mother-of-pearl. Mother-of-pearl is made of nacre, the same material that coats a pearl. Nacre is usually a pale colour, though the nacre lining the shells of Tahiti can be dark.

Where the layer is thick enough, mother-of-pearl can be fashioned as beads, spheres or domed cabochons, but mostly thin layers are used, for example, as low relief decorative pieces.

Shells that have layers of different colours may be fashioned as cameos. The outer layer is cut away to reveal an inner layer of a different colour. Examples include the pink and white of the conch, and the spider conch (Lambis lambis), the mottled cream and brown of the tiger cowrie (Cipraea tigres) with the violet inner layer, and the white outer layer of shells (including Cassidae madagascarensii), which have an inner layer of beige or brown.

Cameos

Tortoiseshell

Tortoiseshell was made by warming and flattening the shell of the Hawksbill turtle and was used to produce, for example, tortoiseshell cases, hair combs and brooches. However, since 1973 this turtle has been an endangered species and the sale of tortoiseshell has been banned.