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Pearl Education

Pearls and their Lustre


Lustre is a term that refers to the deep, luminous glow on the pearls surface that is visible to the human eye. It’s occurrence is caused by light reflecting and refracting off the outer layers of the pearls surface, known as it’s nacre. The overall quality and thickness of the nacre will help determine how iridescent and brilliant a pearls lustre will be. Lustre is considered the single most distinguishing feature that pearls have over all other gems. Not only does Lustre affect the overall look of pearls but is also affects the value considerably.


A pearls outer skin is refereed to as the surface of a pearl, and being a build up of layers of nacre. We have to consider that the pearl is from a living creature underwater, quite often in conditions that are not ideal. The nacre reflects this and commonly displays forms of imperfections on the surface. The surface of a pearl should be considered in two ways.

1. Blemishes – This includes imperfections such as spots, bumps, chips, scratches or wrinkle effects on a pearls surface.

2. Pearl grain – This refers to the structure of the pearl’s skin, depending on how tight the structure is, this will determine how visible the pearl grain is. The tighter the structure, the grain will appear less evident and produce a higher Lustrer

A Pearls Surface
Pearl Shapes


Even with today’s cultured pearls, their overall shape can vary substantially. 

It’s probably no surprise to hear that the most sought after and highly valued pearls are those that are perfectly spherical or round.  In fact a very small percentage of cultured pearls turn out perfectly.

Shapes include:

  • Round – A perfectly round sphere. A pearl is considered round when the variation in its diameter is less than 2.5%. For example, a pearl measuring 10mm can have up to 0.25mm variance but is still classed as round.
  • Near round – Very slightly imperfect shape, although the pearl may look perfectly spherical to the human eye, a pearl is considered near round when the variation in its diameter is more than 2.5%.
  • Drop – A water droplet shaped pearl will always have a longer vertical axis than horizontal axis. Pearls that fall within this category are those in the shape of a teardrop, oval or egg shape.
  • Button – Opposite to drop shaped pearls, the vertical axis of a button pearl will always be shorter than its horizontal axis.
  • Baroque – A baroque pearl is considered asymmetrical or free formed or flowing and can be extremely unique. When one side of a baroque pearl is round or symmetrical it is considered semi-baroque.
  • Circle – A pearl is classified as a circle pearl when parallel grooves, bands or rings are running around the outside of the pearl.


This section of our pearl education is fairly self explanatory. All pearls are measured in millimeters (mm), using a extremely accurate calibrated measuring instruments. In most circumstances pearls are simply measured by their outside diameter. Size contributes to a pearls value. The overall size of pearls varies with every species of Pearl Oyster. Pearls can range from a small 3mm to very large over 20mm. Very large Pearls are often only seen in South Sea or Tahitian due to their large oyster shells.

Me Jewellery proudly offer you the Central Coast’s Broken Bay Akoya Pearls which vary in size from 6mm to 10mm

Off-Round, Drop, Button and Baroque pearls  are usually measured from their widest point and their longest point. Although some measurements seen via the internet show some irregularity in how they measure pearls like these.  One other technique that is used, is called sieving!, where pearls fall through a serious of holes of certain sizes

Pearl Education 1
Pearl Colours


The colour of a pearl is actually primarily determined by the species of the oyster that it grows in, however the environmental conditions and water quality in which they are grown can also determine a pearl’s colour and skin texture.

South Sea pearls derive their magnificent colour and exceptional lustre from the Pinctada Maxima or Silver/Gold lipped oyster. The Pinctada Maxima generally produces pearls in shades of White, Ivory, Silver and Blue with brilliant iridescent overtones of Pinks and Greens, however it can also produce the natural gold range of pearls with shades of Cream, Yellow, Champagne and Gold.

Tahitian pearls occur naturally in a remarkable range of colours from Aubergine, Peacock, Green, Grey, Blue to a deep Black all with various overtones. Tahitian pearls are produced by the Pinctada Margaritifera or Black lipped oyster.

Akoya pearls produce a vast array of radiant shades of White, Cream and Ivory. A natural gift from the Pinctada fucata martensii oyster, Akoya pearls are famous for their magnificent, deep Pink overtones. It also should be noted that Akoya pearls are quite often dyed to enhance their colours.

Central Coast’s Broken Bay Akoya pearls produce an extraordinary range of colours that are Naturally Produced. Their colours are from deep silver blue and running through to silver pink, silver white, white champagne and gold.

*Images: The images used- on this page are borrowed from other sources and are not associated with Me Jewellery. We are using these images as ‘Fair Use’ by education and will remove them if requested to do so.