LEXA’s price index is based on purity and perfection. The ultimate in class. The finest class of natural untreated royal blue sapphire, “pigeon blood” red ruby, and imperial green jadeite. Just as LBMA prices Gold on the basis that it is 99.99% pure. The reason many of the 10 gems LEXA prices have not been uniformly priced before was because much of the scarcest jadeite has been carved into beautiful statues and jewellery, since some of the greatest sapphires sit atop tiaras and rings, the objective pure value of these gems is heightened. Likewise, purest jadeite or a stunning emerald fashioned irretrievably into a piece of lesser art diminishes its value. Artistic and aesthetic value cannot be determined by a price index.

For the best valuations gems require testing and valuing by professionals, especially for Jadeite, Chinese Hetian “Mutton-Fat” Jade and Tianhuang Stone require more precise testing with experience and some advanced scientific laboratory tests:

Energy-Dispersive X-Ray Spectroscopy (EDS)
Fourier-Transform Infrared Spectroscopy (FT-IR)
X-Ray Diffraction (XRD)Scanning Electron Microscopy (SEM)
Scanning Electron Microscopy (SEM)

Take Jadeite as an example. The big issue with jadeite is has it been resin-impregnated? The current test method used in most commercial labs for testing jadeite to see if they are resin-treated is only based on the FTIR test which has made mistakes on its identification.

There are several cases that occurred in recent years of some old jadeite items from the Qing dynasty (1644 to 1911) being given the wrong test result. The reason is that

FT-IR spectroscopy is a highly surface-sensitive technique with significantly higher sensitivity to the presence of trace contaminants (i.e., impurities or coatings distributed at the surface), jadeite is polycrystalline material, many organic materials detected by the FTIR test may have been caused by old polishing organic wax or human skin oils left on the material during hundreds of years of handling – not by modern resin treatment.

LEXA’s testing process is much more comprehensive in testing for resin impregnation, designed using FT-IR spectroscopic analyses, in combination with X-ray diffraction (XRD), also analysing by a combined scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS analyses) for micron-scale elemental variability, correctly detect resin impregnation treatment.

Tourmaline

Sapphires

Jadeite

Alexandrite

Rubies

Emeralds