Monday, 22 September 2014

Pearls - Natural and Cultured

Nature has always provided mankind everything for its survival and sustenance. The abundance that nature has bestowed upon us can be seen all around. Not only our basic needs have been taken care of but we have also been gifted with gems and minerals. These gems and minerals have been unearthed by humans for thousands of years now for personal adornment and industrial purposes.


This post of SDI talks about one such gem which has been conferred upon us by nature – Pearl!
Pearl is an organic gem which is found inside a mollusk and is coated with a substance called nacre which is the secretion of this marine animal. Usually the mollusks which form pearls have two shells. And natural pearls are formed without any human assistance.
 The process of pearl formation is one of the most interesting phenomenon that mankind has ever come across. Usually when the mollusks open their shells to feed and take oxygen an irritant or a foreign particle enters. This foreign particle enters the reproductive system of the mollusk and causes irritation.  The mollusk responds by secreting a substance called nacre. Secretion results in creation of many concentric layers of nacre, which in due course creates a pearl. The nacre is made up of calcium carbonate and contains a substance which is able to hold the nacre together – chochiolin. Nacre is what gives a pearl its characteristic lustre. Nacre is also known as mother-of-pearl which forms the iridescent lining of the shell.

Cultured pearls can be defined as pearls which have been formed with the help of human interference in the natural process. Almost all the pearls which are used for making jewelry today are cultured. Cultured pearls usually are harvested with the help of a process termed as bead nucleation. Also it requires another mollusk which is called the ‘sacrificing mollusk’ and it lends its lining tissue to the other mollusk in which the bead will be planted. Under this process a bead nuclei which is actually a shell, is surgically implanted in the reproductive system of a mollusk know as gonad along with the lining tissue.  This bead nucleus forms the very core of the cultured pearls. This surgery is conducted by experts and it takes a time of 2-6 years to harvest the pearls.
There are two different categories of cultured pearls – saltwater pearls and freshwater pearls.

Saltwater pearls are cultured in water bodies with relatively high salt content like oceans, seas, rivers etc. and take 2-3 years to harvest. There are three types of saltwater cultured pearls:
Akoya Pearls: Akoya pearls are considered to be first completely spherical pearls which appeared in the market in the 1930’s. These pearls have a mirror like lustre and are cultured with the oyster named pinctada fucata martensii which are usually found off the seas of Japan and China. Their size ranges from 2mm – 7mm in diameter. Classic Akoya pearl is white in colour with a pink overtone. Akoya pearls also come in pink, champagne, silver and gold tones. The highest quality of Akoya pearls is called hanadama pearls.


South Sea Pearls: south sea pearls are majorly cultured in Australia, Indonesia and the Philippines and in the mollusk called pinctada maxima. Their size ranges from 8mm – 18mm and they have a soft, satin like lustre. South sea pearls come in many shades like white, gold, black and black with different overtones.


Tahitian Pearls: these pearls are usually grown in black-lipped oysters called pinctada margaritifera. Tahitian pearls are commonly called black pearls. The body color is usually black with overtones of pink, green, violet and blue. These pearls are usually harvested in Cook Islands and French Polynesia and range from 8mm-17mm.

Freshwater pearls are cultured in freshwater bodies like lakes, ponds and rivers. A freshwater mollusk can produce up to 50 pearls at a time which greatly helps in bringing down the cost of pearls. They are relatively cheaper than saltwater pearls. Also, freshwater pearls do not use a bead nucleus to produce pearls. Rather they use only a piece of lining tissue from freshwater sacrificing mussels, so these pearls are made of 100% nacre and due to this reason they are the closest to natural pearls. The process to harvest these pearls can take as long as 4-6 years. Freshwater pearls have a rather soft lustre. The highest quality freshwater pearls are called freshwater orient pearls. The mussel that produces freshwater pearls is called hyriopsis cumingi and a few other species like margaritifera margaritifera. These pearls are majorly cultured in China and on a smaller scale in US and Japan.


Besides, these saltwater and freshwater pearls one might even come across terms like Keshi pearls, Mabe´ pearls or Abalone pearls.

Keshi Pearls: these pearls are accidental by-products of pearl farming and are supposedly formed both in freshwater and saltwater pearls. These pearls form under two circumstances. Firstly, when the bead nucleus is rejected by the mollusk and what remains is the tissue donated by the sacrificing mollusk. As a result, pearl sac is created. Secondly, the donated tissue gets dislodged accidentally and again the pearl sac is formed.


Mabe´ Pearls: mabe´ pearls are commonly referred to as “half pearls” or “blister pearls”. These are grown in Akoya, South Sea, Tahitian and Freshwater mollusks but the most famous species in which they are grown are- ptera sterna, ptera penguin and pinctada maxima. These are grown in a slightly different manner. The bead nucleus is planted between the outer shell and the inner lining of the shell and hence it grows like a blister. Later, the blister is cut out, the bead is removed and the hollow area is filled with filler and covered with a mother-of-pearl backing. These take 2-3 years to culture and are most suitable for earrings and necklaces.


Abalone Pearls: abalone is a single shelled mollusk and is famous for its unusual iridescent colour. Most abalone pearls are baroque (irregular shape). It is difficult to culture abalone pearls because they are haemophiliac. Natural blister pearls form on the shell. They display a beautiful array of colours like pink, green and blue.


One has to admit that pearls are one of the finest creations of nature. It is a versatile gem and its soft lustre is timeless. Its subdued glow is like the light of the moon and represents delicate emotions like love and romance. Pearls for sure add a magical touch to one’s life.

*The Author is a Colored Stone Graduate from Gemological Institute of America, Mumbai and a Diamond Graduate from Solitaire Diamond Institute, Bangalore. She also holds a Diploma in Jewelry Designing & Manufacturing from Jewelry Product Development Centre, Jaipur. She also blogs at 'The Jewel Affair'

*Picture Courtesy: Google Images