For the gemmologist the refractometer is the most important gem tester after a loupe. It measures refractive index (to what extent light is bent as it passes through the gemstone).
This product is intended for gemmologists (or those about to study gemmology) - instructions are not included.
Approx. 5 X 3 X 2 inches.
Range: 1.30 to 1.81
Possible error in readings: +/- 0.01
Test plate made of high-refractive glass
Power: Takes 3 size LR44 batteries (included).
2ml of contact fluid is included, just to get you started, but you will eventually need to buy a full bottle (10ml).
Is it easy to use?
BASIC OPERATION: Rest the flat polished surface of the stone on the test plate, and through the viewfinder you see a scale, part of which will be light and part of which will be dark. In between the light and dark is the 'shadow edge' that marks a reading on a scale. It's a little slow and fiddly but not too difficult to master.
ADVANCED OPERATION: Not only do you get a reading, but often you will see two shadow edges, indicating a doubly refractive stone (which, itself, is diagnostic), AND advanced users can glean further information by rotating the stone to see if either or both of the shadow edges move, and by taking minimum and maximum readings for each.
Although this is an 'easy' test because you end up with a number, and you look up the number on standard charts, you will soon discover that (as with all gem testers) there are many gemstones with the same (or overlapping) readings. A refractometer will help you narrow the possibilities to a handful (maybe one or two) stones, but it will not give an instant 100% guaranteed answer.
Some stones are out of range for this machine (their refractive index is too high to be measured) including some garnets, diamonds and most diamond simulants including zircon and sphene. This cannot, therefore, be used as a diamond tester.
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