PRESIDIUM PGI-TD5612 Mode D'emploi page 7

III. About your Presidium Gem Indicator (PGI)
The Presidium Gem Indicator is an enhanced and more
convenient handheld version of the Presidium Gem
Tester/Colored Stone Estimator based on the invention
of Professor Julian Goldsmid from the University of New
South Wales in Australia. It was developed to distinguish
between diamonds and other colored gemstones using
the principles of thermal conductivity.
Most colored gemstones have their individual color
and distinguishable heat conductivity properties, with
diamonds having the most exceptional heat conductivity.
The Presidium Gem Indicator probe consists of two linked
thermometers: one, which is heated electronically, while
the other is cooled by the gemstone being tested. The
difference in temperature creates an electrical output,
which is then amplified and displayed on the new digital
organic LED (OLED) display.
The Presidium Gem Indicator is further able to give
indication about the possible colored gemstone
through its color separation capability. As some colored
gemstones have similar thermal conductivity, the addition
of the color separation feature will thus be able to give
a more definitive indication about the type of colored
gemstone.
With this, the Presidium Gem Indicator is now capable
of identifying a wider range of up to 31 gemstones
compared to the previous desktop Presidium Gemstone
Tester/Colored Stone Estimator.
It is to be noted that PGI still does not distinguish between
natural and synthetic gemstones, including diamonds
against moissanites, as they have similar physical
properties (thermal conductivity and color).
The Presidium Gem Indicator has been subjected to
thorough factory quality control, and will generally give a
clear and reliable reading of the gemstone being tested
under proper use. However, you are advised to conduct
further supporting tests.
4