Types of Pearls

1. cultured pearls:

Freshwater cultured pearls offer an enormous variety of shapes and sizes, which is why they are popular all over the world. The size of the freshwater cultured pearls varies from 2 - 8mm, the average measures approximately 4 - 5mm. Rarely freshwater cultured pearls with a size of more than 10mm are found. Cultivation of those charming pearls dates back until the 13th century. The famous Japanese 'Biwa' pearls used to control the industry from 1924 until well into the 70's. The Biwa Lake in Japan, like so many others, became a victim of environmental pollution caused by adjoining factories and urban sprawl. The extensive freshwater pearl production in the waters of Lake Biwa came to an end.
China started its freshwater pearl production just before 1970. Over the years, a more and more remarkable quality was achieved. Today Chinese freshwater cultured pearls dominate the market.
"Hyriopsis schlegeli" is the most commonly used mussel for freshwater pearl cultivation, belonging to the species of Unionides. The outer shell an ordinary brown, the inside yet a glossy white. The maximum size of this mussel may reach 30 x 20 cm. Freshwater cultured pearls, contrary to saltwater cultured pearls, do not contain a mother of pearl nucleus. Pearls exceeding a size of 8mm are an exception. One mussel can be implemented with 20 to 60 implants to grow freshwater pearls. After approximately one and a-half years have passed, the pearls have grown to a size of 3mm. After three years, sizes of 7mm are possible. A larger size can be achieved only, if the mussel remains untouched for more than 4 years.
Freshwater cultured pearls appear in a wide range of colours: white, off-white, champagne, shades of pink and orange, purple, mauve, silver and brown. Their unique shapes cover oval, ovate, button-shaped, and drop shaped. Some show a stunning similarity to potatoes. Perfectly round, large freshwater cultured pearls are a rare gem.

2. Akoya pearls

Since oysters are relatively small, the average size of Akoya pearls (Saltwater Pearls) varies from 2 to 9 mm. Originally cultured in Japan, the so-called Akoya pearls were the most popular saltwater pearls for almost a century. Until the 90’s the production was controlled by Japanese companies. As from 1990, China started cultivating Akoya pearls in remarkable quantities which meant serious competition for Japan’s production fairly soon. Pinctada fucata martensii, is the nomenclature for the double-shelled mussel of the species Pteriidae, used to cultivate Akoya pearls. Just like freshwater pearl production, the saltwater pearl cultivation starts by implanting a perfectly rounded mother-of-pearl nucleus along with an irritant into the oyster. Only two, maximum four nucleuses can be hosted at the same time, while freshwater pearl cultivation allows implantation of several more. Tahitian pearl cultivation allows one nucleus per mussel only. After the harvest, Akoya pearl producing mussels will not be nucleated again. Untreated Akoya pearls are mainly cream coloured, yellow or green. The pearls displayed in shop-windows are the result of a sophisticated treatment applied to eliminate impurities. Shapes vary from ovate, button-shaped, drop-shaped to baroque. The Value of Akoya pearls depends on their size, shape, colour and luster, as well as on the composition of their surface. For necklace of exceptional quality made of pearls measuring 8-9 mm, one has to part with a couple of thousand dollars.

3. Tahitian pearls:

The major feature of black Tahitian pearls is their large size. Black Tahitian pearls belong to the group of South Sea pearls and can measure between 9 and 17 mm. A thick and healthy mother-of-pearl layer around the implanted nucleus creates an immaculately natural colour, luster and beauty. These black pearls do not require any artificial improvement, which is why they are admired as the "Queen of pearls".
South Sea pearls are divided into two main categories: bright and dark. A mussel called 'Pinctada maxima' is used to cultivate the bright pearls. According to the shells remarkable size – Pinctada maxima can weigh up to 5 kilograms – a respectively large pearl can grow inside it. Black South Sea Tahitians are cultivated in a mussel called Pinctada margaritifera. Due to the species outstanding qualities, Tahiti’s dark pearl production is considered as the world’s best.
Contrary to freshwater and saltwater pearls, only one nucleus per mussel can be implanted. Many live oysters reject their irritant though. Only a small percentage of harvested South Sea pearls will be perfectly round. Those pearls come in a wide range of colours: bright silver, shading to dark gold, a variety of pink, cream, champagne, yellow, green and blue. Furthermore, pitch-black, iridescent peacock-overtones, darker shades of green, blue, brown, red and yellow may occur. Black Tahitian pearls achieve a top-price level worldwide. For an immaculate necklace you will have to spare a couple of ten thousand dollars. Generally the darker the Tahitian black pearl, the more valuable it is.