GÜBELIN - GEM LAB - Pearl Reports

This is the identification number of your report. It allows us to determine when and where your item was examined. It is also a means of establishing whether or not the report is authentic. When communicating with us on an existing report, we need this number to track down its details.

This usually corresponds to the date of the analysis. In the case of a duplicate report, this date reflects when it was issued, not the date of testing.

In order to ascertain the exact weight of a pearl, we use a highly accurate scale. The unit of measurement used for the weight of a pearl is a carat or grain. One carat is equal to one fifth of a gram, i.e. 0.2 grams or four grains. The measurement in carats is given to two decimal places, the measurement in grains to one decimal place.

Pearls are rarely perfectly round. Some of the best-known shapes are round, teardrop, oval, button and baroque.

A micrometer is used to measure accurately the dimensions of a pearl. The measurement unit we use is millimetres; each measurement is given to two decimal places. If what is being measured is a strand of pearls, the report will state the measurement range of all the pearls, or indicate a range only.

The colour of a pearl is often difficult to perceive. What appears to the eye as white, yellow, pink, green, blue, purple, brown or black consists of a combination of body colour and overtone.

Body Colour
The tiny aragonite crystals of each nacre layer are held together by an organic substance. This often contains a pigment, which essentially originates from the host mollusc. This would explain, for example, the grey to black colour of black-lip oyster pearls.

Overtone
Even though a pearl might already seem to have a distinct body colour, very often a hint of another colour is visible cascading over the surface – this is the ‘overtone’ (also known as a ‘secondary’ or ‘physical’ colour). The overtone is created when the light passes through pearl’s layers. However, depending on the thickness of these calcium carbonate and organic material layers, one or several of the secondary colours may be more prominent. Overtone shades are usually pink, green, blue or purple.

This is where we state whether the pearls are natural or cultured. Cultured pearls are created by inserting a small piece of tissue (with or without a bead) into the mollusc.

This is where we report on whether the colour of a pearl is natural or treated. The appending of an Appendix or Note page is usually mentioned in the Comments section.

Each of our pearl reports comes with a photograph taken by our photographer in the laboratory. The high-resolution photos are true to scale and approximately true to colour.