How Do I Get Started in Gemology?


This page is meant to be a resource to anyone who has just started looking at gem identification and needs a little help figuring out what to do next. Maybe you bought some gemstones in a parcel and are now wondering what they really are. You or a friend recently came into some jewelry and want to get an idea of what they are without spending $100 per piece for an expert. This guide will help you get started. Below is a list of gemological identification instruments in order of difficulty to use. The first instrument is the easiest to use and the last instrument is the hardest to use. Difficulty is defined as the amount of time required to practice or the level of experience needed to make the instrument useful.

Gemology Instrument Overview
Instrument Measures Gemstone Specificity Usability Mounted Gemstones? Detect Synthetics? Gem Rough?
Refractometer Refractive Index High Easy No No No
Specific Gravity Kit Density High MediumNo No Yes
Hannemann Gem FiltersLight Absorption Low Easy YesYes Yes
Polariscope Optical Axis Low Easy YesPartly Yes
Dichroscope Color of Optical AxisMediumMediumYesNo Yes
Microscope Inclusions / Growth LinesMediumMediumYesYesYes
Spectroscope Light Absorption High Hard YesYes Yes

  1. 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.
  2. Specific Gravity:
    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.
  3. 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!
  4. 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. .
  5. Spectrocope:
    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.