The Pocket Spectroscope: A Quick Guide For Gemologists

The spectroscope is used in many fields. Gemologists use spectroscopes to see a gem's absorption spectrum. Learning how a gem interacts with light is a major step to identifying a stone and even determining if it's natural or synthetic. An inexpensive pocket spectroscope is useful for aspiring students as well as professionals who need to identify specimens, including rough, while away from their labs. “Midvale Company employee Frank Caesario Jr. using spectroscope to observe steel color and gauge temperature, June 1952” by Kheel Center is licensed under CC By 2.0
The spectroscope is used in many fields, from astronomy to industry.  Portable models, like the one used above by Mr. Caesario, are very useful.  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. “Midvale Company employee Frank Caesario Jr. using spectroscope to observe steel color and gauge temperature, June 1952” by Kheel Center is licensed under CC By 2.0

Question

My granddad was a gemologist. When he passed away 10 years ago, 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?

Thanking you in advance,

Adam

Answer

I recognize this device. It’s a pocket spectroscope and stand made by Orwin Products Ltd.

The spectroscope is a fundamental tool for gemologists. To use this instrument, line up these things in this order: light source, stone specimen, pocket spectroscope, and 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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Middle school students and their families learn about spectroscopes. “Middle School Mad Science” by NASA Goddard Space Flight Center is licensed under CC By 2.0