Ocean Treasures: A Guide to Every Type of Pearl and Their Significance 

The go-to for the classic strand necklace, there’s no doubt that Akoya pearls are the most famous pearl of the bunch. Produced by the Pinctada fucata oyster, also known as the Akoya pearl oyster, they are farmed primarily in Japan and China and prized for their brilliant lustre. Their near-perfect roundness is achieved by implanting a small bead nucleus and mantle tissue into the oyster, a technique brought to commercial scale by Mikimoto in the early 20th century. Most fall between 3mm and 9mm in size and usually take between 10 and 18 months to form. White and cream are the classic colours, but grey-blue, silver-blue and even gold also exist.

South Sea pearls are among the largest cultured pearls in the world, grown by the Pinctada maxima – the largest of the saltwater pearl oysters – in the warm waters of Australia, Indonesia, the Philippines, and Myanmar. The thick layers of nacre – the iridescent substance secreted by the oyster that forms both the pearl and the mother-of-pearl lining of the shell – that build up over up to around three years of growth give South Sea pearls a unique milky glow. White and silver are the colours most associated with this variety of gem, produced by the silver-lipped variety of the oyster, with Australia the dominant source of the finest examples. The gold-lipped variety of the same oyster, meanwhile, produces the warm golden South Sea pearls, with the Philippines, particularly around the islands of Palawan, home to some of the finest examples.

During cultivation, an oyster sometimes rejects its implanted nucleus, but rather than stopping there, the remaining mantle tissue continues secreting nacre regardless – the result is a keshi pearl, formed with no core at all. Being composed almost entirely of nacre gives keshi pearls a dazzling lustre. Having no nucleus to dictate a shape means they grow however they choose, producing organic forms that are impossible to predict. Keshi means “poppy seed” in Japanese, a nod to their teenier size, and these pearls usually emerge in smaller quantities than standard cultured pearls.

Japan’s Lake Biwa was once the historic centre of freshwater cultured pearl production, and the pearls it produced were unlike anything else, often flat, elongated, with a distinctive high lustre that set them apart from the rounder varieties coming out of China. That era is largely over as pollution and environmental damage severely reduced production, and genuine Biwa pearls are now pretty rare and historically significant.

Only around one in every 10,000 to 15,000 Queen conch – a sea snail found in Caribbean waters – produces any pearl at all, and fewer than 10 per cent of those pearls are gem quality, meaning only around one in 100,000 to 150,000 conchs yields a gem-quality example. That rarity alone would make them remarkable, but the pearl itself is equally unusual, being non-nacreous, with a porcelain surface and characteristic flame pattern, and at its finest displaying a vivid rose pink.

Abalone are farmed in significant numbers around the world, but for their meat and their shell, not their whole pearls, which form rarely and are not commercially cultivated at scale in the same way as other pearls. When they do occur, in Haliotis molluscs found off coasts including California, New Zealand, South Africa, and Japan, they carry the same extraordinary iridescence as the shell itself, with electric shades of blues, greens, and purples.

The quahog clam is best known as an ingredient in New England chowder, which makes it an unlikely source of one of the rarest pearls in the world. Found along the US East Coast, the quahog occasionally produces a pearl in deep lavender to purple, a colour derived directly from the clam’s shell pigmentation and found almost nowhere else in such a vivid hue. It cannot be commercially cultured; every example is entirely natural, and gem-quality pieces are extraordinarily scarce. The clam’s cultural significance also predates any interest in its pearl by centuries, as the quahog shell was used to create wampum, the shell beads and belts used by Indigenous peoples of the Northeastern Woodlands for ceremonial or social purposes.