| Selection of gemstones over the whole range of possible refractive indexes. |
 |
This instrument is not available anymore. Calibration was difficult and had to be done manually. |
3 identical Gemmeters were used for this test. Calibration is difficult and has to be done manually. |
The new digital refractometer did not exist when this test was conducted. It has an automatic calibration mode and comes with 2 calibration stones. Readout is more precise. |
Fire Opal
Reference: 0
Weight: 1.57 ct
Polish quality: bad Average value:
Difference in %: |
Krüss Refractometer 1.390
1.390
1.390
1.390
1.390
1.390
1.390
1.390
1.390 |
Jemeter Digital 90 1.511
1.511
1.518
1.514
1.511
1.510
1.503
1.515
1.512
8.75 % |
Gemmeter A 1.483
1.485
1.485
1.485
1.485
1.485
1.487
1.485
1.485
6.83 % |
Gemmeter B 1.464
1.466
1.469
1.466
1.466
1.466
1.466
1.469
1.467
5.50 % |
Gemmeter C 1.485
1.483
1.483
1.483
1.485
1.485
1.485
1.485
1.484
6.78 % |
Blue values are within the tolerance of traditional tables. Note that the value given by the Krüss Refractometer is low. The Jemeter is to high and the Gemmeter also reads to high. |
Amethyst
Reference: 11.2
Weight: 7.31 ct
Polish quality: medium Average value:
Difference in %: |
Krüss Refractometer 1.548 1.548
1.548 1.551
1.548 1.555
1.548 1.548
1.549 |
Jemeter Digital 90 1.561
1.569
1.568
1.573
1.572
1.570
1.573
1.563
1.569
1.25 % |
Gemmeter A 1.551
1.551
1.551
1.551
1.551
1.551
1.551
1.551
1.551
0.11 % |
Gemmeter B 1.531
1.533
1.533
1.533
1.533
1.533
1.536
1.533
1.533
-1.04 % |
Gemmeter C 1.543
1.543
1.538
1.543
1.543
1.543
1.543
1.541
1.542
-0.46 % |
|
Glass
Reference: AD
Weight: 1.37 ct
Polish quality: good Average value:
Difference in %: |
Krüss Refractometer 1.520
1.520
1.520
1.520
1.520
1.520
1.520
1.520
1.520 |
Jemeter Digital 90 1.548
1.546
1.547
1.546
1.545
1.546
1.546
1.546
1.546
1.73 % |
Gemmeter A 1.518
1.516
1.518
1.514
1.518
1.518
1.521
1.518
1.518
-0.16 % |
Gemmeter B 1.509
1.504
1.504
1.504
1.504
1.506
1.506
1.506
1.505
-0.96 % |
Gemmeter C 1.516
1.518
1.518
1.516
1.518
1.521
1.518
1.518
1.518
-0.14 % |
|
Feldspath
Reference: AA
Weight: 0.64 ct
Polish quality: medium Average value:
Difference in %: |
Krüss Refractometer 1.520 1.525
1.520 1.525
1.525 1.525
1.520 1.525
1.520 1.525
1.520 1.525
1.525 1.525
1.520 1.525
1.523 |
Jemeter Digital 90 1.542
1.545
1.543
1.542
1.541
1.542
1.540
1.540
1.542
1.23 % |
Gemmeter A 1.533
1.536
1.531
1.536
1.533
1.536
1.536
1.536
1.535
0.76 % |
Gemmeter B 1.521
1.521
1.521
1.521
1.521
1.521
1.521
1.521
1.521
-0.14 % |
Gemmeter C 1.536
1.536
1.533
1.533
1.533
1.533
1.533
1.531
1.534
0.68 % |
|
Beryl Heliodor
Reference:
Weight: 4.24 ct
Polish quality: good Average value:
Difference in %: |
Krüss Refractometer 1.568 1.570
1.570 1.570
1.568 1.570
1.568 1.570
1.570 1.570
1.568 1.570
1.568 1.570
1.570 1.570
1.569 |
Jemeter Digital 90 1.590
1.590
1.586
1.585
1.587
1.586
1.588
1.587
1.587
1.15 % |
Gemmeter A 1.570
1.570
1.570
1.570
1.570
1.570
1.568
1.570
1.570
0.02 % |
Gemmeter B 1.553
1.553
1.553
1.553
1.553
1.555
1.555
1.555
1.554
-1.00 % |
Gemmeter C 1.565
1.565
1.565
1.565
1.563
1.565
1.565
1.565
1.565
-0.29 % |
The Jemeter reads high. |
Topaz
Reference: 08.2
Weight: 3.08 ct
Polish quality: very bad Average value:
Difference in %: |
Krüss Refractometer 1.615 1.625
1.620 1.628
1.620 1.628
1.618 1.628
1.620 1.628
1.620 1.625
1.615 1.625
1.618 1.625
1.622 |
Jemeter Digital 90 1.620
1.618
1.616
1.610
1.613
1.609
1.619
1.619
1.616
-0.42 % |
Gemmeter A 1.605
1.605
1.595
1.598
1.585
1.600
1.605
1.605
1.600
-1.39 % |
Gemmeter B 1.580
1.583
1.588
1.585
1.583
1.583
1.585
1.583
1.584
-2.38 % |
Gemmeter C 1.600
1.595
1.608
1.600
1.603
1.600
1.595
1.605
1.601
-1.33 % |
A badly scratched surface gives a low reading with the Gemmeter. Surprisingly the Jemeter is not that much affected. |
Andalusit
Reference: K
Weight: 0.47 ct
Polish quality: good Average value:
Difference in %: |
Blue Chart tables 1.639 1.642
1.635 1.642
1.640 1.642
1.640 1.645
1.635 1.640
1.635 1.640
1.639 1.642
1.640 1.645
1.640 |
Jemeter Digital 90 1.635
1.624
1.631
1.629
1.627
1.643
1.634
1.628
1.631
-0.53 % |
Gemmeter A 1.623
1.626
1.626
1.626
1.628
1.628
1.628
1.626
1.626
-0.83 % |
Gemmeter B 1.608
1.608
1.605
1.610
1.610
1.610
1.610
1.610
1.609
-1.90 % |
Gemmeter C 1.613
1.618
1.615
1.621
1.621
1.615
1.621
1.615
1.617
-1.38 % |
This stone was very small and therefore hard to place correctly on the Gemmeter. |
Turmalin
Reference: Y
Weight: 1.06 ct
Polish quality: good Average value:
Difference in %: |
Krüss Refractometer 1.620 1.635
1.622 1.635
1.635 1.635
1.630 1.635
1.620 1.635
1.635 1.635
1.630 1.635
1.620 1.635
1.631 |
Jemeter Digital 90 1.639
1.639
1.633
1.640
1.647
1.640
1.634
1.635
1.638
0.47 % |
Gemmeter A 1.623
1.628
1.621
1.618
1.610
1.613
1.610
1.615
1.617
-0.83 % |
Gemmeter B 1.603
1.608
1.605
1.610
1.608
1.608
1.610
1.610
1.608
-1.41 % |
Gemmeter C 1.615
1.615
1.613
1.615
1.613
1.615
1.618
1.621
1.616
-0.93 % |
|
Spinel
Reference: 09.2
Weight: 0.87 ct
Polish quality: good Average value:
Difference in %: |
Krüss Refractometer 1.710
1.710
1.710
1.710
1.710
1.710
1.710
1.710
1.710 |
Jemeter Digital 90 1.715
1.719
1.717
1.717
1.719
1.717
1.720
1.718
1.718
0.45 % |
Gemmeter A 1.714
1.708
1.717
1.717
1.717
1.717
1.717
1.717
1.716
0.32 % |
Gemmeter B 1.698
1.695
1.695
1.695
1.695
1.698
1.698
1.695
1.696
-0.81 % |
Gemmeter C 1.703
1.706
1.706
1.706
1.706
1.706
1.706
1.708
1.706
-0.24 % |
|
Chrysoberyll
Reference: AC
Weight: 1.51 ct
Polish quality: good Average value:
Difference in %: |
Krüss Refractometer 1.748 1.750
1.748 1.751
1.748 1.751
1.745 1.750
1.747 1.750
1.750 1.754
1.750 1.754
1.748 1.750
1.750 |
Jemeter Digital 90 1.748
1.755
1.746
1.750
1.750
1.757
1.751
1.749
1.751
0.06 % |
Gemmeter A 1.763
1.760
1.760
1.760
1.760
1.760
1.760
1.760
1.760
0.61 % |
Gemmeter B 1.750
1.750
1.747
1.747
1.750
1.750
1.750
1.747
1.749
-0.04 % |
Gemmeter C 1.765
1.765
1.763
1.760
1.763
1.760
1.763
1.788
1.766
0.93 % |
|
Synthetic ruby
Reference: R
Weight: 7.59 ct
Polish quality: medium Average value:
Difference in %: |
Krüss Refractometer 1.765 1.770
1.761 1.770
1.764 1.770
1.770 1.770
1.765 1.770
1.761 1.770
1.764 1.770
1.770 1.770
1.768 |
Jemeter Digital 90 1.772
1.775
1.770
1.768
1.773
1.769
1.769
1.761
1.770
0.12% |
Gemmeter A 1.778
1.772
1.774
1.774
1.770
1.774
1.770
1.772
1.773
0.31 % |
Gemmeter B 1.763
1.765
1.765
1.763
1.765
1.768
1.768
1.765
1.765
-0.13 % |
Gemmeter C 1.768
1.768
1.765
1.765
1.768
1.768
1.765
1.765
1.767
-0.06% |
|
Saphir blue-yellow
Reference:
Weight: 1.62ct
Polish quality: medium Average value:
Difference in %: |
Krüss Refractometer 1.762 1.770
1.768 1.770
1.770 1.770
1.766 1.770
1.761 1.770
1.765 1.770
1.770 1.770
1.763 1.770
1.768 |
Jemeter Digital 90 1.763
1.758
1.760
1.764
1.760
1.758
1.761
1.761
1.761
0.41% |
Gemmeter A 1.772
1.772
1.772
1.770
1.772
1.774
1.772
1.772
1.772
0.24% |
Gemmeter B 1.750
1.750
1.750
1.753
1.753
1.753
1.757
1.753
1.752
-0.87 % |
Gemmeter C 1.768
1.757
1.740
1.757
1.772
1.757
1.717
1.760
1.754
-0.81% |
|
Saphir light-blue
Reference: HEX
Weight: 1.11 ct
Polish quality: very bad Average value:
Difference in %: |
Krüss Refractometer 1.761 1.770
1.762 1.770
1.762 1.770
1.761 1.770
1.761 1.770
1.761 1.770
1.761 1.770
1.761 1.770
1.766 |
Jemeter Digital 90 1.773
1.770
1.770
1.774
1.778
1.771
1.772
1.773
1.773
0.40 % |
Gemmeter A 1.788
1.788
1.792
1.792
1.798
1.786
1.788
1.788
1.790
1.38 % |
Gemmeter B 1.782
1.776
1.782
1.782
1.782
1.776
1.778
1.776
1.779
0.77 % |
Gemmeter C 1.790
1.794
1.788
1.786
1.796
1.796
1.784
1.790
1.791
1.41 % |
Tiny fractures and inclusions reaching the surface give a high reading. |
Garnet
Reference: 01.1
Weight: 0.50 ct
Polish quality: medium Average value:
Difference in %: |
Krüss Refractometer 1.799
1.799
1.799
1.799
1.799
1.799
1.799
1.799
1.779 |
Jemeter Digital 90 1.808
1.804
1.849
1.850
1.852
1.824
1.837
1.808
1.829
1.67 % |
Gemmeter A 1.800
1.804
1.829
1.798
1.802
1.819
1.811
1.796
1.807
0.47 % |
Gemmeter B 1.815
1.850
1.800
1.815
1.811
1.852
1.802
1.817
1.820
1.18 % |
Gemmeter C 1.794
1.831
1.821
1.788
1.786
1.786
1.794
1.788
1.799
-0.03 % |
|
Zirkon
Reference: C
Weight: 2.47 ct
Polish quality: good Average value: |
Blue Chart tables
1.780 - 2.025
|
Jemeter Digital 90 1.968
1.952
1.938
1.943
1.953
1.925
1.968
1.952
1.950 |
Gemmeter A 1.915
1.902
1.900
1.909
1.909
1.906
1.922
1.917
1.910 |
Gemmeter B 1.913
1.926
1.926
1.924
1.924
1.924
1.924
1.917
1.922 |
Gemmeter C 1.933
1.933
1.935
1.928
1.937
1.935
1.939
1.933
1.934 |
|
Cubic Zirconia
Reference: reference stone
Weight: 2.00 ct
Polish quality: good Average value: |
Blue Chart tables
2.150 - 2.18
|
Jemeter Digital 90 2.218
2.183
2.184
2.179
2.193
2.187
2.176
2.175
2.187 |
Gemmeter A 2.168
2.193
2.180
2.175
2.182
2.171
2.204
2.180
2.182 |
Gemmeter B 2.197
2.186
2.164
2.156
2.154
2.177
2.156
2.208
2.175 |
Gemmeter C 2.164
2.146
2.199
2.156
2.154
2.154
2.212
2.166
2.169 |
This is the reference stone delivered with the gemmeter. Note: all 3 gemmeter tested have a slightly different calibration. This indicates that the procedure to calibrate is tricky. |
Diamond
Size : 3.7mm
Weight: 0.18 ct
Polish quality: good Average value: |
Blue Chart tables
2.417
|
Jemeter Digital 90 2.525
2.656
2.843
2.632
2.932
2.867
2.655
2.783
2.737 |
Gemmeter A 2.470
2.470
2.454
2.420
2.461
2.439
2.445
2.420
2.447 |
Gemmeter B 2.415
2.448
2.429
2.473
2.505
2.511
2.448
2.401
2.454 |
Gemmeter C 2.423
2.480
2.476
2.439
2.602
2.483
2.468
2.476
2.481 |
This stone was to small and very difficult to place on the gemmeter. |
Moissanit colorless
Reference:
Weight: 0.24 ct
Polish quality: good Average value: |
Blue Chart tables
2.648 - 2.691
|
Jemeter Digital 90 2.635
2.644
2.623
2.654
2.647
2.645
2.652
2.654
2.644 |
Gemmeter A 2.671
2.676
2.676
2.676
2.687
2.687
2.686
2.687
2.681 |
Gemmeter B 2.635
2.639
2.642
2.635
2.645
2.639
2.635
2.642
2.639 |
Gemmeter C 2.652
2.655
2.652
2.649
2.652
2.649
2.652
2.652
2.652 |
|
Moissanit black
Reference: AE
Weight: 1.09 ct
Polish quality: medium Average value: |
Blue Chart tables
2.648 - 2.691
|
Jemeter Digital 90 2.699
2.694
2.696
2.686
2.697
2.694
2.694
2.702
2.695 |
Gemmeter A 2.713
2.719
2.724
2.708
2.719
2.708
2.719
2.724
2.717 |
Gemmeter B 2.676
2.681
2.681
2.676
2.681
2.676
2.681
2.787
2.692 |
Gemmeter C 2.713
2.713
2.713
2.713
2.708
2.708
2.708
2.713
2.711 |
|
Serial number of the Gemmeters used during the test.
Starting values of the Gemmeter after a 2 minute warm up time. |
Gemmeter A
SN0502167452
1.259 |
Gemmeter B
SN0501157434
1.251 |
Gemmeter C
SN0501157431
1.256 |
|
Procedure
- Only faceted stones have been tested.
- A Krüss Refractometer was used to measure the standard RI value for each stone.
- A heat up time of 2 minutes for the Gemmeter was allowed before taking measurements.
- Each stone has been cleaned with a chamois before taking the measurements.
- The chamois was washed and dried before first use according to the instructions of the manual.
- Each table was inspected with a 10x loupe prior to measuring.
- Eight positions of each stone have been measured and the average was calculated.
- This was then compared with the average of the refractometer readings and the difference was calculated in %.
- 9 out of the 19 stones were tested a second time two days later. All results were confirmed.
- The BLUE CHART tables of Mister Nicolas Hervé Lazzarelli were taken to compare the results for stones with a RI higher than 1.81
- The double refraction was not taken into account.
- The database function was not tested.
Conclusion
- The Gemmeter has the same drawbacks as the Jemeter digital 90 had. It is very sensitive to the quality of the polish and cleanliness of the stone.
- All stones appear birefringent, this is due to small irregularities in the polish and dust particles.
- The use of the gemmeter in combination with a polariscope is recomended.
- Stones smaller than 4 mm with a table less than 3 mm in diameter are too small to be measured.
- Unlike a refractometer the gemmeter always displays a result. Some readings may be way off due to surface scratches, dust or inclusions reaching the surface.
- It takes some experience to recognise a wrong read out.
- The big advantage over the refractometer is, you need no contact liquid and you can measure stones up to an RI of 3.000
- The database does not make a lot of sense as you can not enter values like color, transparency or birefringence to limit the field.
- The database has also a bug and suggests tourmaline up to RI 1.77
This is an independent test by Hubert Heldner Montreux April 11th 2005.
You use the Gemmeter at your own risk and responsability.
Back to the digital refractometer. |
