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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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Refractometer Instructions - Step by Step
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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.
Replacement Batteries: LR44 button batteries (Energizer® 357 Battery is
one brand name.) You will find them in the watch / calculator battery
section of drug stores, Wal-Mart, K-Mart, and probably your grocery store.
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| 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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5
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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. |
Determining Bifringence
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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Thank you for shopping
with Pretty Rock.com!
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