Calcium Carbonate Particles & Parasites
The scientific explanation for natural pearls is almost as mystifying as folklore. This organic gem of unsurpassed beauty and elegance is composed entirely of calcium carbonate particles assembled in overlapping layers and bound together with organic material by oysters, which are members of the mollusk family of sea creatures. When an irritating foreign particle which could be a piece of sand, or a parasite enters the oyster, the creature responds by covering the irritant with smooth layers of body material and an iridescent layer called ‘nacre’ which builds up in layers to become a pearl. Gem quality pearls are produced by a variety of saltwater, non-edible oysters and freshwater oysters.
Grains & Grams of Oriental Pearls
Unlike other gems, pearls are measured by weight in a unit called a ‘grain’, and by size in millimeters. There are four grains in a carat and 20 grains in a gram. Pearls are differentiated on the basis of origin. Completely oyster-made pearls are referred to as ‘natural’, and ‘Oriental’ pearls are natural saltwater pearls from the Persian Gulf which, until a century ago, was the primary source of pearls in the world and ‘seed-pearls’ measure just 2 millimeters or less in diameter.
The term ‘French pearl’ was adopted to identify irregular pieces of oyster shell possessing certain characteristics of natural pearl. ‘Freshwater pearls’ come from oysters living in rivers and ‘cultured pearls’ are made with the help of mankind, by means of introducing a carefully placed and precisely designed foreign particle to sea-living oysters.
Pears, Buttons, Tears & Rounds
Round or perfectly regular pearls are the most widely known and commercially most valuable of all, but only one of the many natural shapes which include pear, egg, tear-drop, button and Baroque.
Black, Grey, Blue, Green, Bronze & Pink Pearls
The colors of pearls vary from light to dark in a wide range of body colors and a variety of overtones. Light pearls manifest soft shades of pink, white or cream and overtones of blue, green, red, pink and gray. Dark pearls, referred to collectively as ‘black pearls’ encompass silver gray, dark blue, purple, blue-green, green and bronze, with and without metallic overtones. In general, colors are more common in freshwater than in saltwater pearls.
Middle Age Natural Phenomena
In the Middle Ages, when so much explanation of life was ascribed to natural phenomena, the colors of pearl gained particular meaning and significance:
Gold pearl was an emblem of wealth
White was an emblem of idealism
Black was an emblem of philosophy
Pink was an emblem of beauty
Red was an emblem of health and energy
Gray was an emblem of thought…