How to Identify Colored Gemstones

If you’ve been out there shopping flea markets and estate sales for fine jewelry, you’ve probably found items with colored gemstones. But are they real, synthetic or glass?

In this post we’re going to take a look at colored gemstones with regard to:

  • Different types of colored gemstones
  • What to look for; What to look out for
  • Tools, instruments and how to use them
Different Types of Colored Gemstones

Did you know that not all blue stone are sapphires, not all green stones are emeralds and not all red stones are rubies. Regardless of the color you choose, there are – in most cases – at least three gemstones available in that color. And tourmalines come in literally hundreds of different hues. For more information on colored gemstones visit The  Compendium.


This is made even more confusing by the fact that there are old-type synthetics as well as more modern synthetics out there that are extremely difficult to distinguish from the natural gem. So lets take a look at some gemstone basics.




What to Look For – Inclusions in Colored Gemstones

Since some inclusions are unique to certain gemstones, learning the types of flaws – for genuine stones and synthetics – can be valuable in identifying a colored stone.

Bubbles – these inclusions can be of different sizes and shapes. Round bubbles usually appear in synthetics – but may be found in natural amber. In synthetic ruby or sapphires, these bubbles may be round, in a string with a large bubble at the center and smaller bubbles on each side, or pear- or tadpole shaped. For pear and tadpole shaped bubbles, the tails will point in the same direction. If there are numerous bubbles, ‘gemstone’ is probably in glass. But, if there are only a few, you’ll need to investigate further to see if it actually a bubble or if it is a crystal. Crystals can appear to be bubbles using a 10x loupe. You’ll definitely need to investigate further.

Cleavage Fault – is a break in the stone rather than an inclusion. Having a cleavage fault may cause the stone to break apart.

Curved Straiae – concentric curved lines found in older-type synthetic sapphires and rubies.

Feather – is a crack either inside the gemstone or breaking the surface. Having this inclusion makes the stone susceptible to damage. Note: Numerous cracks on the surface of a stone thought to be an emerald – where the cracks are in a web-like pattern – will probably mean the stone is a synthetic.

Flash Effect – (in emeralds) appearance of a flash of orange or yellow that changes to blue as you tilt the stone back and forth is an indication of epoxy-resin filler.

Halo Inclusion – flat, disc-like inclusions resulting from the growth of a crystal inside the host stone (i.e., Zircon inside Sapphire). This inclusion is also found in genuine garnets.

Internal Growth Patterns – most often provide a clue to synthetics. These patterns may look like mountain peaks.

Silk or Fiberlike Inclusions – look like fine needles and can be found in genuine sapphire, ruby, garnet and aquamarine.

Swirl Marks – curved, swirled lines found in glass. Note: You’ve probably seen these swirls in the glass panes used in old furniture doors.

Twinning Planes – appear as parallel cracks resembling panes of glass lying in parallel planes. Found in both rubies and sapphires, these cracks can crisscross at 60 and 120 degrees. While they prove the gemstone to be genuine, they can also make it weak if there are too many.

There are many more things to look for in identifying colored gemstones.  For those desiring more in depth information, Gem Identification Made Easy, Fourth Edition: A Hands-on Guide to More Confident Buying & Selling is an excellent reference.  It is full of pictures (some colored), good diagrams and illustrations, plus lots of descriptions on how to identify colored gemstones.




Tools, Equipment, Instruments

One could easily invest thousands of dollars in buying equipment for identifying gemstones but we’re going to take a look at the basics for practical use and to maintain a reasonable budget.

10X Triplet-Type Loupe   – often referred to as the jeweler’s loupe, this item is necessary to detect cracks, chips, scratches, cut and inclusions in gemstones. There are many types available, but for gem identification – the loupe must be 10X Triplet-Type with a black casing. Do not buy one with a shiny metallic finish.

How to Use a Loupe

  • Hold the loupe between your thumb and forefinger. With the other hand hold the stone to be examined in much the same way.
  • Bring the loupe close to your eye, bracing the hand against your face.
  • Bring the object to the loupe.
  • Brace both arms on a table or against your chest for steadiness.
  • If examining an unmounted gemstone, hold it by the edge (girdle) – do not touch the top.
  • Rotate the gemstone and slowly tilt it to view from different angles. This allows your eye to focus on all areas of the stone as you look for flaws.
  • Focus on both the surface and the interior by changing the viewing distance from the loupe.
  • When looking for inclusions, wiggle a finger up and down behind the gemstone to create shadowing and brightening effects inside the gemstone. This will help to make viewing inclusions better with regard to size, color and shape.

Dark-Field Loupe  – much like the jeweler’s loupe, this instrument is also 10X. To use this instrument, it is placed on top of a small maglite – and you’re ready to examine the gem. Being able to view the gemstone against a black background – with lateral illumination vs. light being transmitted through the bottom of the gemstone – makes it easier to see inclusions and their type. This is especially true for finding fracture fills.

Chelsea Filter – a pocket-sized filter used to spot fakes mixed in with natural gemstones.

When it comes to identifying colored gemstones, this is just a very small look at what’s involved and what one needs to know. However, if you plan on buying or investing in  jewelry, it pays to be able to identify the different colored gemstones – and distinguish them from the synthetics and glass ones out there.



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