What are the main characteristics that define the value of a pearl?
The nacre thickness and absence of irregularities provides the pearl with its beauty. A top quality pearl has a thickness of at least 0.4 mm.
This characteristic is derived from the reflective property of light through the various layers of nacre. The clearer and sharper the impression reflected by the pearl, the higher its value. Normally it ranges from a weak luster to a discrete luster to good or top quality luster for the most valued pearls.
The cleaner the surface of the pearl, the greater its value. It should be taken into consideration that a pearl of good quality always has some small flaws. This can range from pearls with apparent blemishes or circles, to those completely free of flaws to the naked eye.
Pearls can vary between 1 mm to 20 mm (for South Sea pearls). The most common sizes range between 6.0 to 7.0 mm; for subsequent sizes prices rise considerably for each increment of 0.5 mm.
A perfectly spherical pearl is considered a rarity; only 5-10 % of pearls collected have a high degree of roundness. Other pearls have varied shapes: oval, drop-shaped, button, ringed and baroque.
Colour does not provide added value to the pearl; it is a simple matter of taste, but it is important to assess the overtones and/or alterations induced. Eliotis Perle checks and measures the fluorescence of pearls by using UV rays.