You can quickly identify most gemstones by looking at a few simple characteristics, such as color and weight. If you want a deeper and more precise identification, though, you'll need to use special tools to examine the inside of the stone.
Steps
Part 1 of 4: Using Identification Tables
Step 1. Invest in a gemstone identification chart
If you think you will need to identify gemstones often, your best bet is to invest in a printed chart or manual.
If in doubt, look for a book or chart authorized by the Gemological Institute of America (GIA)
Step 2. Search the internet for simple tables
If you only rarely have to identify gemstones, you may be able to get away with using specific tables on the internet. These tables are much less detailed and complete, but they can work without anything else.
- You can use the Hiddenite Gems identification chart when you know color and hardness:
- You can use the Gem Select RI table when you know refractive index and birefringence:
- The American Federation of Mineralogical Societies (AFMS) offers a free table of the Mohs Scale:
Part 2 of 4: Verify that the Stone is a Gemstone
Step 1. Touch the surface of the stone
A stone with a rough or sandy texture should not be considered a gemstone.
Step 2. Check for malleability
A malleable stone - that is, one that is easy to shape with a hammer, crushing or bending it - is probably a metallic mineral and not a true gemstone.
Real gemstones have a crystalline structure. You can shape these structures with cuts, fractures and abrasions, but they have fixed planes that cannot be altered by simple pressure
Step 3. Learn which materials are not classified as gemstones
In particular, pearls and fossilized wood may be mistakenly classified as precious stones, but they do not fall into this category in the strictest sense of the term.
Step 4. Beware of synthetic materials
Synthetic stones share the same structure, chemical composition and physical properties as natural counterparts, but are created in the laboratory and not by nature. You can identify a synthetic stone by looking at several characteristics.
- Synthetic stones often have curved, non-angular growth patterns within the stone.
- Round and long striped gas bubbles are often an indication of conciseness, but be careful, as gas bubbles are also present inside natural stones.
- Platinum or gold platelets can adhere to synthetic stones.
- Fingerprint inclusions are common in synthetic stones, as are nail-shaped inclusions, V-shaped growth patterns, veiled spherical inclusions, and inner columnar structures.
Step 5. Beware of imitations
An imitation stone is a material that resembles a real gemstone at first glance, despite being made from a completely different material. These stones can be natural or man-made, but there are some good techniques you can use to identify them either way.
- The surface of an imitation may appear pitted and uneven, like an orange peel.
- Some imitations have vortex marks known as flow lines.
- Large, round gas bubbles are common in imitations.
- Imitations are often lighter than their natural counterparts.
Step 6. Determine if the gemstone is an assembled stone
The assembled stones are made with two or more materials. These stones may consist entirely of natural stones, but synthetic materials are often added.
- Use a flashlight to illuminate the stone when looking for signs of assembly.
- Look for differences in sheen and colored or colorless assembly lines.
- Also look for the red ring effect. Turn the stone over and look for a red ring on the outside. If you spot the red ring, it's probably an assembled stone.
Part 3 of 4: Simple Observations
Step 1. Observe the color of the stone
Color is often the first clue. You can divide this analysis into three parts: tone, color and saturation.
- Do not light the stone to analyze its color unless it is a dark stone and you need to determine if it is black, dark blue or some other color.
- Color refers to the general color of the stone's body. Be as specific as possible. For example, if a stone is a yellowish green, identify it as such and don't just write "green". The GIA has identified 31 colors for the stones.
- Tone refers to the brightness of the color, i.e. light, medium, dark or an intermediate tone.
- Saturation refers to the intensity of the color. Determines if the color is warm (yellow, orange, red) or cold (purple, blue, green). For warm colors, look for brown tones in the stone. For cool colors, look for gray shades. The more brown or gray the stone, the less saturated the color is.
Step 2. Observe the transparency
Transparency describes how light filters through the gemstone. A stone can be transparent, translucent or opaque.
- Transparent stones are those in which it is possible to see completely through (example: diamonds).
- It is also possible to see through translucent stones, but colors or veils alter the image (example: amethyst or aquamarine).
- It is not possible to see through opaque stones (example: opal).
Step 3. Check the weight or the estimated specific gravity
You can determine the weight of a gemstone by bouncing it in your hand. This is a quick and easy way to estimate the weight of a stone without performing complex specific gravity tests.
- To judge the weight, bounce the stone in the palm of your hand and ask yourself if it feels heavy or light for its size.
- Specific gravity measurements are rather obsolete as a practice among gemologists, and weight measurements are preferred as a relatively accurate estimate.
- Aquamarine, for example, has a low weight, while the similar-looking blue topaz is heavier. Likewise, diamond has a lower weight than synthetic cubic zircon.
Step 4. Note the cut
While this is not a foolproof identification method, some gemstones are more likely to be cut in a few ways. Often, the ideal cuts are determined by the way the light bounces off the crystal structure of the stone.
The most common cut styles you will encounter are brilliant, rose, stepped, scissor and emerald. For each of these basic styles, there are also sub-styles
Part 4 of 4: Detailed Study of the Precious Stone
Step 1. Ask yourself if you can run damage tests
There are some identification tests that you should avoid if you are to preserve the integrity of the gemstone. These include the examination of hardness, grain and cleavage.
- Some stones are physically harder than others, and hardness is usually measured with the Mohs scale. Use the different substances provided in the hardness kit to scratch the surface of the gemstone. If the stone can be scratched, it is less hard than the substance you used to scratch it. If the stone cannot be scratched, it is harder.
- To examine the grain, drag the stone onto a ceramic plate. Compare the grain left by the stone with that of a table.
- Splitting refers to the way a crystal breaks. If you notice any splinters on the surface, examine the area inside the splinters. Otherwise, you will have to hit the stone hard enough to break it. Ask yourself if the area is rounded like the rings of a shell, straight like steps, grainy, chipped or uneven.
Step 2. Check for optical phenomena
These phenomena occur only inside some stones. According to the stone, you may observe color changes, asterisms, moving bands of light or other.
- Check for optical phenomena by passing the light of a flashlight over the surface of the stone.
- Color changes are one of the most important optical phenomena, and you should check them for each stone. Look for color changes between natural light, incandescent light, and fluorescent light.
Step 3. Observe the shine
Gloss refers to the quality and intensity with which a surface reflects light. When performing a luster test, reflect the light on the smoothest part of the gemstone.
- To check the luster, turn the stone, allowing the light to reflect off the surface. Observe the stone with the naked eye and with a 10x lens.
- Determines whether the stone looks dull, waxy, metallic, shiny (adamantine), glassy, greasy or silky.
Step 4. Observe the scattering of the gemstone
The way a stone separates white light into the colors of the spectrum is called dispersion, and the visible effect of dispersion is called fire. Examine the amount and intensity of this "fire" to identify the stone.
Light the stone with a torch and examine the fire inside. Ask yourself if the fire is weak, medium, strong or extreme
Step 5. Determine the refractive index
You can examine the refractive index (IR) using a refractometer. Using this device, you will be able to measure when the light path is altered within the stone. Each gemstone has a precise IR, so finding a sample's IR will help you identify it.
- Place a small knob of IR fluid on the metal surface of the refractometer near the back of the crystal half cylinder (the window where you will put the stone).
- Place the stone face down on the fluid and slide it towards the center of the semi-cylindrical crystal using your fingers.
- Look into the magnifying glass. Keep observing until you see the outline of a bubble, then look at the bottom of this bubble. Take the measurement from there, rounding the decimal places to the nearest hundredth.
- Use the magnifying glass for a more specific reading and round the result down to the thousandth.
Step 6. Consider a birefringence test
Birefringence is related to IR. To perform a birefringence test, you will need to turn the stone on the refractometer six times during the observation period, and note the changes.
- Do a normal IR test. Instead of holding the stone steady, gradually rotate it 180 °, in six 30 ° rotations. For each rotation, measure the IR again.
- Subtract the lowest measurement from the highest to find the stone's birefringence. Round to the nearest thousandth.
Step 7. Check for single or double refraction
Use this test on transparent and translucent stones. You can determine if the stone is single refraction (RS) or double refraction (RD) only for easier identification. Some stones can be classified as aggregates (AGG).
- Turn on the light of a polariscope and place the stone face down on the lowest lens (polarizer). Look through the upper lens (analyzer), turning it until the area around the stone becomes darker. This is the starting point.
- Rotate the analyzer 360 ° and see how the light changes around the stone.
- If the stone appeared dark and remained dark, it is probably an RS stone. If the stone appeared clear and remained clear, it is probably an AGG stone. If the stone has gone from light to dark, it is probably RD.
Advice
- Clean the gemstone with a special cloth before examining it. Fold the cloth in quarters and insert the stone inside. Rub it firmly between the layers of the cloth using your fingers to remove dirt, fingerprints and oil.
- Hold the stone with tweezers when you examine it to avoid getting it dirty.
