| Refractometer | This instrument is wonderfully simple to use. It will give you the refractive index of a gemstone.
What the heck is that? The refractive index is a precise measurement of how much the gemstone bends light
when it enters the stone. Why is that important? Very few gemstones will bend light by the same amount!
So this is a great way to narrow down the possibilities when identifying a gem.
| |
Specific
Gravity Kit | After the refractometer nothing comes close for ease of use and strength of identification. This is
actually easier to use than a refractometer, but the messy setup and scale needed to use it make it second.
This test will give you the density of the gemstone relative to water. Much like the refractive index, a
gemstone's density is very unique. I often tell people that if they get the refractive index (RI) and the
specific gravity (SG) they should know precisely what the gem material is. Then they can worry about whether
or not it is synthetic or has been treated.
| |
Hannemann
Gem Filters | Gem filters are easy, practical, but unorthodox gemological instruments. This is because the
gem filters give clues rather than facts. Gemstones and their synthetics will show a completely
different color under the filter. They do this by giving you a quick and easy reading of the types
of light absorbed by the gem. For example synthetic emerald shows red through the filter,
but natural emerald does not. However, you mustalready know that the gemstone is emerald or
that it is topaz, aquamarine, etc. Only then will the synthetic differentiation be useful to you.
The hanneman gem filter set comes with a set of instructions and charts to follow.
| |
Polariscope | The polariscope has many uses. It can detect refractivity, identify polarity,
and reveal the optic signature of the gemstone. The first use is most common, as you simply place the
gemstone between the two gray discs called polarized filters. Then you rotate one of the filters in a full circle
and count the number of times the stone changes from light to dark. That is the refractivity of the gemstone.
What the heck is that? Refractivity relates to the crystal structure of the gemstone. As a stone is formed
in the earth, it will either have one axis or two axis. A few stones even have three axis. The number of
changes from light to dark is where the crystal axis lines up with the polarized filters and allows light through.
Knowing the number of axis helps narrow down the type of gemstone and really helps when you are debating between
two specific types of materials. For example, whether it is topaz or garnet. Garnet has single axis and topaz has double axis.
But don't get too confident of your deducation, spinel is single axis too, and aquamarine is double axis. Blue stones
can be troublesome to pinpoint because there are a lot of possibilities. This is why gemologists love charts!
| |
Dichroscope | The dichroscope does two things at once. First is shows you two little squares of color. Your job is to
decide if those two colors match or not. If they always match, then you know it is a single axis stone.
If they don't match and you have two colors, then it is a double axis stone. Three colors means three axis.
Now, the colors that you see help you to know the type of gemstone. Again you need a chart for all those colors and
which gemstone they point to. If you are color blind, give up. If you are not very good at color differentiation, prepare
to spend a good bit of time training your eyes. I grab a set of stones I know the identity of and practice that way.
| |
Spectroscope | If you lack patience and fortitude, back away slowly. Spectroscopes are not for the lighthearted, the fun loving, or
the me generation. This instrument was forged in the fires of grueling hard work, dogged persistent, and a certain
amount of satisfaction from inflicting pain on oneself. That said, it is a a wonderful tool if you are the rare human
being that doesn't mind really learning how to do something that takes work, persistence, and real effort. That excludes
about 95% of the human race. Once the spectroscope has been mastered by the remaining 5% of us, it shows which light
frequency are absorbed by the gem material. Huh? Okay, everyday light when you step outside is generally "white light".
White light is composed of all the colors of light, from red, orange, yellow, green, blue to purple. Think rainbows!
The spectroscope has a really cool prism device (called diffraction grating) that splits white light up into its component
lights that make up the rainbow. Then, when you put the gemstone in the way of the white light, some portions of the
rainbow are blacked out. Those portions are absorbed or blocked by the gemstone. That is called the absorption spectra
of the gemstone. Once again, you need a chart to help you see which spectra matches which gemstone.
|
|
