Natural pearls: birth and chimical composition

Natural pearls birth and chimical composition

For a long time natural pearls have had a mysterious aura around their birth, told in a fairy tale-like and magic way, involving dewdrops, floating mussels and divine rays.

The reality is a lot more different and – unfortunately – it has nothing in common with this dreamy fairy tale: these precious and natural rarities are born from the casuality as a collateral reaction of a foreign body.

The penetration of any sort of corpuscles (like a fragment of sponge) produces an immediate – but diluted in time – reaction which forces the mussel to excrete that precious substance called mother of pearl which covers the foreign body, stopping the irritation and forming unconsciously at the same time a treasure.
This birth without the human help makes natural pearls really rare and appreciated thanks to their thicker and more luminous layer of nacre which praises itself with particulare perlescences and iridescences.

Once formed, the pearl awaits only human eyes to be found and finally become part of a marvelous jewel which will adorn the neck of a lucky woman that will enjoy the ancient and mysterious beauty radiated by these gems born form the soul of the nature.

But, going deeper, what is it made up of? A what are its specific characteristics?

Here is a detailed table with all its scientific chacateristics that define the composition of the natural pearl:

Chemichal composition: aragonite and calcite (82-92%), conchiolina (4-14%), water (2-4%).
Chemical formula: CaCO3 + conchiolina.
Crystalline system: aragonite crystallizes in the rhombic system, and calcite in the trigonal one.
Crystalline forms: small crystals oriented with concentric structure (aragonite and calcite).
Color: white, pink, yellow, black but also blue, brown and green.
Density: about 2,66.
Refraction index: from 1,530 – 1,690.
Brightness: from pearly to metallic.
Transparency: matt.
Hardness: from 2,5 to 4,5.
UV rays fluorescence: pearls can be inert or reveal a blue, yellow, green or rosy fluorescence if exposed to 366 nm UV rays; the black varieties show instead a pink to reddish fluorescence if exposed to the same radiations.

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