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| How to Use a Refractometer |
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A refractometer measures the angle at which light rays refract (or bend) as they move through a gemstone, and giving a reading (R.I. or Refractive Index) from a scale seen though the eyepiece of the refractometer. Because R.I. is unique for each type of stone, it helps to identify most stones. However, it can not distinguish between natural and synthetic stones. It is used most easily with stones that have at least one flat, polished surface. As with most refractometers, this refractometer reads to 1.81. It will not work for stones with a higher R.I., such as diamond, some diamond imitations, and certain varieties of garnet. These instructions are for the refractometer we sell, but should work with most refractometers.
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| Label | Description | Instructions |
| 1 | Batteries |
The first time you use your refractometer, insert batteries text up into battery case. Tightly close battery cover over batteries for good connection. Press power switch to turn on refractometer. The refractometer takes 3, 1.5V button batteries. |
| 2 | Hemicylinder | Open upper cover and examine hemicylinder. Hemicylinder should be clear of any dust or film from previous use or factory. If hemicylinder needs to be cleaned, use a little water and a soft cloth. Caution! Dried RI liquid can scratch the hemicylinder. If there is dried RI liquid on the hemicylinder, use a drop of RI to re-wet and dissolve any crystals that may have formed before cleaning. |
| 3 | Stone | Examine the stone to be tested under a bright light. Choose the facet with the best polish and largest surface. This is usually the table of the stone. Be sure the stone is clean, wipe with a soft, lint free cloth to remove any fingerprints or dirt. |
| 4 | RI Liquid | Place a small (very small) drop of RI liquid on the upper end of the hemicylinder. Knowing how much RI to use takes some practice. You need just enough RI to create a good seal between the gem and the hemicylinder. As you test more stones you will learn how much RI is needed for the size of the stone. |
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Place Stone | Place the facet of the stone you have chosen to test on the RI liquid drop and gently pull it to the center of the hemicylinder. Close upper cover if stone is small enough. For very large stones, leave cover open. |
| 6 | Look through eye piece |
Look into eyepiece at about 4-6 inches away so that you can see the scale inside the refractometer. With practice, you will find the right spot to use for your eyes. You may have to hold your head closer or further away from eye piece depending on the stone and your eye sight. |
| 7 | Be a snake charmer! | Slightly move your head, up and down, side to side, and closer and further away from the refractometer until you see a blue-green flash line. (If you feel like a snake charmer, you are doing it right!) This line is usually in between the darker and lighter area on the scale. It is a light sort of teal color line. On bright, clear, clean, well polished stones, the line can be very sharp and clear. For other stones, it is very faint and hard to find. On stone that don’t have a good polish or flat surface, you may not be able to get a reading. If the scale appears dark all the way down to the bottom of the scale, then the stone’s refractive index is too high to read or you have used too much RI liquid. |
| 8 | Take your reading | Read the RI from the higher edge of the blue- green band. RI is read to the nearest hundredth place (eg. 1.65 ) |
| 9 | Use the chart | Compare your finding with a Refractive Index Chart. There is one you can use near the bottom of this page. |
| When you are finished using your refractometer, carefully remove the stone, and clean off the hemicylinder with a soft clean cloth. Store refractometer in case in safe location. RI liquid should be stored away from light in a sealed bottle. Be sure to wash hands after use. | ||
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Some stones are doubly refractive. This property can help you identify your stone. |
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| 1 | Use polarizing filter | While you have a clear reading on a stone following the above directions, unscrew the polarizing filter and place onto the eyepiece. |
| 2 | Rotate Filter | Rotate the polarizing filter to see how much, if at all, the RI reading changes. Write down the RI readings. |
| 3 | Rotate Stone | Rotate the stone about 45 degrees and then rotate the polarizing filter again. Again, write down your readings. Continue this until you have 4 sets of readings. If your stone is doubly refractive, your readings might look like this: 1.770 - 1.774 1.769 - 1.775 1.770 - 1.774, 1.769 - 1.774 (highest and lowest underlined) |
| 4 | Subtract high & low readings | Subtract the highest and lowest of all of your readings. (E.g. Highest 1.775 - lowest 1.769= birefringence .006) |
| 5 | Use chart | Compare your findings to a Refractive Index Chart that has birefringence listed. |
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| The Graduate Gem ID Kit ™ includes the essentials and the extras for studying gemology. Perfect for gemologists who want to identify gems and achieve certification:
Please see item pages for more details about each instrument. Not sure what all these tools do? We offer online tutorials here. Please consider purchasing one of the gemological identification books to help you learn to use your new tools. Sorry, no changes or substitutions can be made to gem kits. -GemKitGrad- Click for more info. |
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| Series M 1.80 +/- .0005 Manufactured by Cargille Labs, Certified refractive index liquid.
Contains 10 grams. Sold by weight, not volume. Bottle is filled to half capacity to avoid spillage. The liquid comes a orangish red color. Caution: Avoid vapor and contact with skin. For use with refractometer only. -SK-2309- Click for more info. |
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| The most popular guide to identifying gems and synthetics. Essential reading for collectors, dealers, and students to avoid mistakes and recognize opportunities. Authors: Antoinette Matlins and A.C. Bonanno Hardcover. 330 pages. -B0676- Click for more info. |
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| 10x high quality optics with three bonded aplanatic and achromatic color corrected lenses that are 20.5mm in diameter. Comes with a deluxe rubber grip for better handling and a highly polished chrome finish. Complete with leather snap carrying case. -gl-10x-20.5- Click for more info. |
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