Many “emeralds” are actually other green gems, green glass, or imitations built from several materials. Conduct several tests before you reach a conclusion one way or the other, since results are not always definitive without specialized gemology equipment. If the emerald, you may also be interested in testing whether it is naturally occurring, or a synthetic laboratory creation.
Evaluating an Emerald
Look for flaws through a magnifying lens or jeweler’s loupe. Examine the gem under magnification, ideally through a 10x triple-lens jeweler’s loupe. Hold it so light strikes it at an oblique angle, in one narrow beam if possible.  If you see tiny flaws or irregular patterns within the stone, it is likely to be a real gem – although not necessarily an emerald. If your gem is very clear, with almost none of these “inclusions,” it may be a synthetic emerald (man-made but real), or not at gemstone at all.
Gas bubbles only appear in natural emeralds near other inclusions of different shapes. If you see a swarm of bubbles alone, the gem is probably glass – but it could be a synthetic emerald.
Check for a sparkling effect
Real emeralds produce little to no “fire,” or colorful flashes that appear under light. If your gem produces a rainbow of flashes, it is not an emerald.
Examine the color
The mineral beryl is only called emerald if it is dark green or blue-green. Yellow-green beryl is called heliodor, and light green beryl is just called green beryl. A yellow-green gem might also be olivine or green garnet.
- The line between emerald and green beryl is blurred / two jewelers could disagree over the classification of a gem.
Look for wear on the facets
Glass and other weak materials wear down quickly. If the edges of the facets look soft and worn, the gem is likely fake.
- Fake glass “gems” often develop a dimpled “orange peel” texture and slightly rounded facet edges. Look for these features under slight magnification.
View the emerald through a dichroscope.
Some gemstones appear different colors from different directions, but you’ll need a cheap tool called a dichroscope to make this obvious. Hold the gemstone very close to one end of the dichroscope while you look through the viewing window. The gemstone must be illuminated by a strong, diffuse light source as white as possible, such as an overcast sky.
Rotate the gemstone and the dichroscope to view it from all directions. Real emeralds are dichroic, appearing blue-green from one angle and a slightly yellow green from another.
Strong dichroism (two very distinct colors) is a sign of a high quality emerald.
It is possible to get unusual results due to an internal reflection off a facet, due to properties of fluorescent light, or due to light reaching the viewing window without passing through the gemstone.
Use this along with other approaches, not as a single, definitive test.
Have the gem appraised.
If you still have doubts, take the gemstone to a jeweler and have it professionally appraised. The jeweler will have access to specialized tools that will give you a definitive answer, along with a lengthy description of your gemstone.
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