Perls – mussel’s or, less often, gastropod’s creations (mailnly Pteria and Pinctada). Made from the same matter as the inside of the shell (nacre, mother of pearl), composed mainly of calcium carbonate (as aragonite) and a horny protein matter (conchiolin), which binds the microcrystals, focused concentrically around the core. Pearls most often appear as a result of the organism’s reaction to presence of an alien object inside the shell. Jewelry defines pearls as „natural organic products, emerged within the pearl of mussels and other molluscs”.
Origin of the name „pearl” is uncertain, but might have come from the species (lat. perna) or the round shape (lat. sphaerula).
Chemical properties: calcium + carbonate + organic matter + water.
Crystal system: (rdiamond) microcrystalline.
Hardness: 2,5–4,5 according To Mosh scale
Density: 2,60–2,85 w g/cm³
Color: white, pinkish white, cream, pink, yellow, grey, dark-grey, black with a green, blue or eggplant reflection, whitish or white-greenish with rainbow reflection, sometimes yellowish or greenish, sometimes pitch black.
Despite relatively low hardness, pearls are crush-resilient.
The size of a pearl varies from pinhead to pidgeon’s egg.
Pearl colors differ depending on the mussel species and the water type.
With the uneven conchiolin distribution, the pearl gains mottling.
1. By color:
White pearls – base color[a] white or close to white with light "orient"[b] or "overtone"[c].
Black pearls (traditional name) – black, close to black or grey; also brown, dark blue, greenish blue or green with graphite reflection.
Brown pearls – black pearl variation, with strong, brown reflection.
Blue pearls – black pearl variation, dark blue to grey-blue toned, due to presence of a conchiolin layer under the surface layer, loam impurity or presence of aragonite impurities with an intensive reflection.
Cream pearls – base color cream, slightly modified by "orient" or "overtone"
Pink-cream perals – base color cream with pink "orient"
Pink perals – base color pink or other with strong pink "orient".
"Fancy" pearls – base color white or cream with pink "orient" blue-green, violet, purple, blue or green "overtone" superimposed on them.
Pink-cream "Fancy" pearls – cream pearls with pink "orient" with the "overtone" afterglow
2. By origin:
Natural pearls – made by nature without human factor both in seas and freshwaters. Described by the name of true pearls, differ to:
Farmed pearls– growing demand resulted in the explosion of mussel farms. Despite such pearls are made with the involvement of human, they are a natural product and not an immitation. As well as natural pearls, differ to sea and freshwater perals.
3. By shape:
Round pearls – specimens typically regularly sphere shaped or slightly flattened.
Baroque pearls – unregularly shaped specimens.
Drop-shaped pearls – specimens shaped like a drop or a pear.
Buton-shaped pearls – specimens not convex, one-sidedly flat.
Grain-shaped pearls – tiny specimens (less than 0,25 gram), asymmetric.
Half-pearls – semi-convex pearls, one-sidedly flattened.
Inter-quartille-pearls – specimens in 3/4 oval, in ¼ flat.
Other pearls: freshwater or colorful.
According to the variety of pearls available on the market, it’s worth to learn:
Pearl’s use & assessment
True and fake pearls distinction
Natural and farmed pearls distinction
Pearls are created by sea mussels, some of freshwater mussels, occasionally by gastropods. Most often they appear as a reaction to an alien matter, wchich got between the mussels’ shell and it’s mantle inside the mantle.
In XIII century China it was discovered that pearls can be farmed by inserting an alien matter, for example a grain of sand. A mussel defends itself by continually laying sequent nacre layers, the same as overstuff the shell. After a few years, a shiny valuable pearl is made. At the turn of the XIX and XX century, the Japanese tackled large-scaled production of farmed pearls.
Already back in the 1761 a swedish naturalist Carl Linnaeus farmed freshwater mussels for their round pearls.
During the XVI and XVII century a significant freshwater pearl fishing center existed in Lower Silesia – obtained material originated from sudetian population of freshwater pearl mussel, a species currently extinct in the area of Poland.
Persian Gulf – pink and white-cream pearls; usually tiny, from 12 g. Main pearl exploitation area -7/8 of world’s production comes from there. Schools extend along the whole Arabian Peninsula, but the most significant are located in the Persian Gulf on the coast of Bahrajn island. The catch conditions in this area are difficult and hazardous.
Mannar Gulf (dividing India from Ceylon) – white-cream pearls with beautiful blue, green or violet "overtone". The pearl catch takes place under the eye of government inspectors, regulating mussel’s output, to prevent overexploitation.
Red Sea Coast – white and white-cream pearls.
Madagascar, Burma, Phillipines, northern Australian coasts – white-silver and yellow-silver pearls, specificly large. Schools extend from southern and north-western coasts of Cape York peninsula to Shark Gulf and along north-eastern coasts of Queenslandu. The biggest income is generated by the sales of nacre, though.
Haiti Coast – round pearls, large (up to 7100g), white with slight "overtone", also yellow, grey and black.
Coast of Florida– the main black pearl catching area; also yellow, greenish and blue.
Central American coastal waters – Mexico and Panama – tiny, inexpensive pearls (also northern coasts of South America.
Coasts of Japan – a number of minor pearl farms, white, slightly greenish; global potentate in pearl farming.
It is estimatedę, that pearls are used as decoration for 6000 years. Round specimens with beautiful shine are highly appreciated in jewelry. Pearls have always been popular; for example, coronation outfit of Barbara Radziwiłł was almost fully covered with them.
Because of the fact, that conchiolin is an organic matter, it is not a sustainable material – easily subject to alteration and decay. Swells when damp, dessicated becomes brittle and breaks down. Pearls therefore „age” and have limited lifespan. "Pearl ageing" can be split to the following stages:
Worn often, pearls may become deformed and deflected from the primal form. Both drought and excesive dampness may harm pearls; also sensitive to acids, sweat (acid pH), cosmetics and hairspray.
Even though prudent care, pearls lose the shine because of the conchiolin decay. Removal of the outer layer doesn’t always give results, in case the decay affected lower layers.
There is no guaranteed lifespan length of a pearl; estimates vary about 100 – 150 years. However, the pearls hundreds of years of age do exist and are presentable. Pearls of old age darken insteel-gray color. Color restoration attempts by lighting did not result in success.
Perls found in ancien tombs fell apart with the first touch, sometimes leaving remains in form of a brown powder.
Regular inspection and upkeep in a special facility may expand peral’s lifespan.
Because of the low hardness, pearls should be worn and stored in such conditions there was not a chance, to touch the surface with metal.