Pearl

Pearl is traditionally associated with health, longevity, wealth, beauty, family love, calm of mind, purity and creativity. Long called “tears of the moon” and “tears of the mermaid”, cherished as a symbol of a woman’s beauty and purity, it is an elegant gem to wear for a lifetime.

It is June’s birthstone. The June birthstones are three — moonstone, pearl and alexandrite (alexandrite added in the December 2021 revision by Japan’s gemstone association). It is also a customary gift for a 12th and 30th wedding anniversary.

No — pearl is not a mineral but is classed as an organic gem. The mineral definition requires being inorganic, natural, with a definite composition and crystal structure; pearl is organic matter (aragonite + conchiolin) formed within a living shellfish, a gem born of a living thing. It belongs to the “organic gem” category with coral, amber and jet.

Its Mohs hardness is 2.5–4, very soft and among the gems that need care. It is sensitive to sweat, cosmetics, perfume, acid (including fruit juice) and alkali, which can cause discoloration and loss of luster. Always wipe it dry with a soft cloth after wear, put it on last after applying cosmetics, store it in its own pouch somewhere with little humidity, and never use an ultrasonic or steam cleaner — and it is a gem that lasts for decades.

The host mollusk and waters differ. Akoya pearl is the Akoya oyster, mainly Japanese (Ise-Shima, Uwajima, Tsushima), white to pink and green. South Sea white pearl is the white-lipped oyster, of the warm seas of Australia, Indonesia, the Philippines, Thailand and Myanmar, large, white to gold. Tahitian black pearl is the black-lipped oyster, of French Polynesia and Tahiti, gray to black, green, purple. Freshwater pearl is mussels such as Hyriopsis, of China (the largest producer) and Lake Biwa, many shapes and colors. Color and size vary with the mollusk.

In 1893, Kōkichi Mikimoto (founder of Mikimoto), from the Shima Peninsula in Mie, achieved the world’s first cultured half-pearl in Ise-Shima. Then in 1907 Tōkichi Nishikawa and others established the round-pearl method — implanting a nucleus together with shell-forming mantle tissue — and Ise-Shima became the first place in the world to produce round cultured pearls. It is the history of Japanese culturing technique rescuing a world pearl industry that over-fishing had driven near extinction in the late 1800s.

Japan (Akoya pearl: Ise-Shima, Uwajima, Tsushima), Australia, Indonesia, the Philippines, Thailand and Myanmar (South Sea white pearl), French Polynesia and Tahiti (black pearl), and China (freshwater pearl, the largest producer) are the main sources. The waters, the host mollusk and the method shift a pearl’s color and character greatly.