Store
>
Click here to enter store
>
Testers
>
Gem Testers
Electronic Gem tester by Presidium
Ref: GEMTEST-PRES
Electronic Gem Tester by Presidium (includes diamond). Tests for ten groups of gemstones. The first five groups overlap on the scale (and they overlap quite a lot): Garnet/Tourmaline/Iolite; Tanzanite/Aquamarine; Chrysoprase/Emerald; Quartz/Amethyst/Citrine.
The next three groups overlap slightly: Jadeite/Spinel; topaz; Ruby/Sapphire.
Finally, one stone gives a very distinctive reading: diamond.
This is a precision instrument and, unlike the diamond-only testers, is extremely sensitive and must be treated as a fragile laboratory instrument - it must be kept clean and dry and must not be bumped or abused. As such it is unsuitable for use by many antiques dealers and scrap merchants.
QUESTIONS AND ANSWERS
Q. Is it easy to use
A. Yes
Q. Does it need checking (calibrating)?
A. Yes - because the readings might 'drift' over the months
Q. If the meter shows the stone might one of half dozen different stones, how do you know which one it might be?
A. You don't
Q. If the stone is one of several dozen stones not listed on the scale, how do you know what it is?
A. You don't
Q. Is there a machine that is guaranteed 100% reliable, costs less than a few thousand pounds and doesn't require a thorough knowledge of gemmology and physics?
A. No - no such machine exists.
CONCLUSION
This is by far the best machine for giving an approximate identification. More usefully, it often tells you what the stone cannot POSSIBLY be. So, for instance, you might be uncertain as to whehter the stone is glass, garnet or tourmaline, but you will know, for certain, that it can't be Spinel, topaz, ruby or sapphire.
Detailed picture of scale
Price: £140.42
£164.99 Including VAT at 17.5%
Quantity:
Chelsea Filter
Ref: CHFILT
Many stones appear to change colour when viewed through the filter. Originally designed for detecting synthetic emeralds, nowadays the Chelsea filter is an invaluable aid to identifying many other gemstones.
To read the instructions manual
click here
and decide for yourself if this is the most valuable tester a dealer could have...or far too complicated to understand!
Price: £20.00
£23.50 Including VAT at 17.5%
Quantity:
Polariscope
Ref: POLARIS
The Item: A tube 80mm tall X 30mm dia.
What is detects: double refraction.
How to use: At the top and bottom of the tube are two filters (Polaroid discs), revolve the top filter until everything in the tube appears dark and place the stone on the platform in the middle (if mounted, you might have to fix the item upright with a spot of blu-tac so that you can see the stone). Now turn the platform so that the stone revolves through 360°.
What you see: If the stone appears to turn light-and-dark it is doubly refractive, if it remains dark it is singly refractive.
For the gemmologist: all crystalline gemstones except for those of the Cubic System are doubly refractive.
For the non-gemmolgist: Moissanite is strongly doubly refractive, diamond is singly refractive. This is, therefore, a very simple and effective method of distinguishing diamond from Moissanite. Instructions: not included.
Price: £17.02
£20.00 Including VAT at 17.5%
Quantity:
Spectroscope
Ref: SPECTRA
The Item: a tube 50mm long X 12mm dia.
What is detects: absorption spectra. How to use: view the colour of a gemstone, either by shining a light (pen-torch) through the stone into the spectroscope if the stone is transparent, or by viewing its reflected light if the stone is opaque.
What you see: a spectrum (rainbow) which might be interrupted with black or white lines, it is the pattern of these lines you must learn to recognise.
For the gemmologist: best at detecting iron and chromium.
For the non-gemmolgist: the 'diamond simulants' YAG and Cubic Zirconia give spectacular spectra and so too does some Zircon. Other gemstones are more difficult to detect. Instructions: not included.
Price: £29.79
£35.00 Including VAT at 17.5%
Quantity:
Store
>
Click here to enter store
>
Testers
>
Gem Testers
