Operating manual for the Gemmeter




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As with all high precision electronic instruments, avoid electromagnetic fields (as mobile phones, motors, transformers, electrical lines, etc.). Protect the sensor opening from dust and moisture.

The gemstones have to be absolutely dry and clean, as this would influence the result considerably. Rub the stone on the enclosed cleaning leather and be aware of the fingerprints you leave when handling a stone.

The gemmeter reaches operating temperature in about 15 seconds once it is switched on with sliding button on the left side.

Place the stone over the sensor opening and cover it with the cap. This is important, as without cap the results will be completely wrong. Take 4 measurements in one position by slightly moving the stone and calculate the average. Then rotate the stone by 45° and repeat, till you have measured 4 positions. This is how you got very precise results.


A less than perfect polish, tiny scratches or dust can falsify the result considerably. It may be difficult to recognize a wrong result as such, without some experience.

The 4 buttons guide you to advanced functions.
Press the menu button . You have 4 options.

  • Gemmeter : for individual measurements. This is preset.
  • Bi-Ref : for double refractive stones when you want to calculate the maximum double refraction. You measure 8 positions while rotating the gem 45° between each position. Press the button to register each value.
  • Show : repeats the last series of measurements.
  • Contrast : to adjust the display.

To verify the precision of the instrument measure with 2 calibration stones from time to time (a CZ is included and a quartz will do the other end of the range).

Once a result is shown you may accede to the database (list of possible stones) by pressing the button. When pressing a second time the scrolling list will be stopped.

With the button the last registered result is deleted.


  • all stones will behave as if double refractive. This is due to tiny irregularities on the surface. Combine the gemmeter therefore with a polariscope.
  • As each double refractive stone behaves as if single refractive in the optical axis, the calculated double refraction may be smaller than in reality. Measure an other facet if the result seems off.
  • Almost all moissanites show a smaller double refraction than they actually have. This is due to the fact that they are orientated for cutting and the table facet is placed perpendicular to the optical axis.
  • The database shows all possible stones, opaque, translucent and transparent mixed together without the possibility to select a stone color. Work with your traditional determination tables for more comfort, as the readout of the gemmeter is calibrated to the sodium standard.
  • Each gemological instrument has its limits. Good practice is to combine different instruments measuring different properties to exclude any error.
  • The big advantage of the gemmeter is that it requires no contact liquid. You can measure refractive indexes between 1.270 - 3.094 with ease.
  • Cabochons or rough stones cannot be measured.
  • A low battery will produce a blinking alarm (low battery).
  • Keep the cleaning leather as clean as possible. You may wash it with soap and cold water, rinse it thoroughly and dry on cold air. Avoid the sun, heat and hot water. Once dry, stretch it, so it gains its flexibility again.


The warranty last for 2 years on material and fabrication errors. The warranty is terminated immediately if you try to repair, open the case, ignore the operating instructions, and usual wear is not covered.

Send the gemmeter to the manufacturer for warranty work. Enclose also a copy of your original receipt and contact the manufacturer before you send in the gemmeter.

Calibration procedure

The gemmeter is carefully calibrated before leaving the factory. Due to a radical different climate or temperatures re-calibration may be necessary.

Before calibration. Verify again the polish and cleanliness of your reference stones, the cleaning leather and the sensor opening. Test also with different reference stones. Cubic-zirconia (RI 2.170±), diamond without inclusions and at least ½ carat in size (RI 2.417), moissanite (RI 2.640 a 2.690) for controlling the high refractive index readout, and take a quartz (RI 1.544 to 1.553) for the low refractive index. It is important to cover the stone with the cap. Take measurements in several positions and do not forget to rotate the stone by 45° each time. If the readout is off, then re-calibrate the instrument with a watchmaker screwdriver 2 - 3 mm and turn the appropriate calibration screw.

For calibration of the high refractive indexes take the lower screw and for the low refractive indexes the upper one. Turn the screw slowly to the right for reducing the readout and to the left to augment the readout. Repeat the process until upper and lower readout are correct.

More information and pricelist here

I wish you a lot of success with the gemmeter. Handle this precision instrument with care and you will get many years of reliable service.
Hubert Heldner   March 2006