Question: My granddad was a gemologist. When he passed away, I inherited many of his things, including lots of gemological instruments. One of these is a mystery to me. It’s a small instrument about 5 cm in length. It has a sticker down the side that reads “OPL England.” At one end is a very fine slit. At the other end is a “viewing hole,” (at least that’s what I think it is). If I look through the viewing end I can see a spectrum. I assume it’s meant to help ID specimens through spectral analysis. But where do I put the stone and the light source?

There’s another bit of kit that this tool seems to fit into. It’s a black plastic contraption. At the top is a hole and another piece of plastic that turns around. This plastic piece has varying sizes of holes around the top.

I hope my description isn’t too vague. Can you help me identify what this is and how to use it correctly?

By International Gem Society 2 minute read
portable spectroscope

Middle school students and their families learn about spectroscopes. Photo by NASA/Goddard Space Flight Center/Bill Hrybyk. Licensed under CC By 2.0.

Answer: I recognize this device. It’s a pocket spectroscope and stand made by Orwin Products Ltd. The spectroscope is used in many fields, from astronomy to industry and also gemology. Portable models are very useful.

What Can a Portable Spectroscope Do?

Gemologists use spectroscopes to see a gem’s absorption spectrum. Learning how a gemstone interacts with light is a key step to identifying it.  This can even indicate if the stone is natural or synthetic. An inexpensive pocket spectroscope is useful for aspiring students as well as professional gemologists who need to identify specimens, including rough, while away from their labs.

How to Use a Portable Spectroscope

The spectroscope is a fundamental tool for gemologists. To use a portable spectroscope, line up these things in this order: light source, stone specimen, the instrument, and your eye. To interpret what you’re seeing, you’ll need to review the basics of spectroscope operation and gemstone identification.

The black contraption is a stand to help you hold stones of various sizes over the opening. There are some tricks to using this.

First, everything has to be held VERY still. Most people prefer using a stand or mount rather than trying to hold the instrument in their hands. (There are even adapters for mounting a pocket spectroscope in a microscope).

Second, you need a lot of light. It takes practice to get enough light through the stone and into the pocket spectroscope to be able to read it. You’ll find the OPL pocket spectroscope isn’t useful for dark stones. Start practicing with something light and one carat or above.

Best wishes,

Donald Clark, CSM IMG

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