How To Appraise A Faceted Gem
(also known as Cut Stones)
To give an accurate appraisal of a faceted gemstone, you need to have a few basics up your sleeve first. You need to know the price of the particular type of stone, what treatments have been applied to the stone, and to take the time to take a closer look at the stone itself using a loupe.
When making your appraisal, you must remember turn the stone around and keep an eye out for any colour change, this generally indicates that the stone is nature. Did you know that Tourmaline often has more than one colour and that Cobalt should have at least two colours!
Remember: Nature isn’t always perfect – you will see flaws within the stone! If not it could be a man made or worth millions!
After awhile, you start to get a feel of a gemstone weight, and the different weights amongst the different types of stones. But carrying an accurate gemstone scale could make all the difference in making the appraisal.
You must know the prices of each gem, sometimes the more rare a stone is the more valuable it could be. You must know what treatments have been done to a gem, its a good thing to ask the seller. Also carry a magnifying glass like a little 10x magnification called a loupe ,it is the best tool to look inside the gem. Don’t worry too much if you see marks with the loupe and not your eye, nature isn’t always perfect.
If a stone is completely flawless with no visible crystal marks or needles or dots or things, then it may mean it is synthetic (or the best gem in the world worth thousands of dollars) and a man is played a part in the making of this stone.
If you handle gems a lot you get to know its weight – like topaz and zircon and sapphire is heavy, some stones aren’t as heavy, also some stones have two colours or three colours if natural, so turn the stone around, is there more than one colour – tourmaline should have more than one colour at different angles whereas a synthetic or heavily treated stone like sapphire that’s been dyed (diffused) with beryllium or cobalt at high temperature may nearly always just be one single colour – which is odd, there should be at least two colours.
So ask what has been done, what treatments, you may need to be good at reading body language to tell a lie from the truth, ask around what seller can be trusted. More than one colour in a stone is referred to as dichroic ( two colours in the same stone) like sapphire. Iolite and Tanzanite is trichroic (meaning three colours visible) ie; iolite shows grey and purple and violet. The dichroism or trichroism isn’t always easily visible.
Look at the gemstone in natural light
Look at the gem in natural light as artificial light or some different lighting can make the gem so much more beautiful, so when moved in natural daylight it could look rather unappealing. Sometimes gem sellers will have the lighting set-up above the gems to optimise their beauty, so be aware of this.
A well trained geologist is taught about how light passes through a stone and may carry small tools to measure light dispersion or light bending from a gem or how a light is shone through, but that is getting technical. If you do your research a few simple things can help, some stones are very bright, some have a more waxy appearance, do some reading and keep absorbing knowledge and it will take some time but some gems start to get recognized as you see more, just by a colour grade, but even to an expert it is very difficult to look at a gem and know exactly what it is unless you can apply a few tools or light tests to it.
For the meantime basic steps can be a big help:
Colour of a gem
For example a certain shade of tourmaline called rubellite can add such high value to an otherwise standard pink tourmaline, and a certain shade of orange/pink in sapphire called papradasha is hugely expensive compared to other colours – even though blue sapphire is the most popular and wanted.
The cut of a gem
How well it is cut, this is where a magnifying glass can come in handy, but don’t be too critical if it looks okay by eye that will usually do, but turn the gem upside down ,does the point of its bottom (pavilion) look straight or is it off to one side when it shouldn’t be, you don’t want to see any chips on the edges of the facets, some stones are brittle like peridot and the sharp edges chip easily and its not a good look and lessens the value. Scratches, on surface? Or having a high polish is better. Don’t be too critical of gems cut under magnification, but its worth a look sometimes. So once you research the price of the market for this year or even month, that each gem is fetching, then think of the old saying below to value a gem.
The 4 C’s of Appraising a Faceted Gemstone
The weight of a gem, a valuable one is of good carat weight thus size (there are 5 carats in a gram). All gems are weighed in carats.
An attractive shade of colour that is well liked, like a shade of apple green in a green garnet (tsavorite) is more prized than a pale green and a brown gem isn’t very popular.
That’s brightness, bright is good (light dispersion, just to be technical). The light goes into the gem, bounces around and gets thrown out so the eye can see a bright look to the gem.
A well cut stone adds value to a gem as it can bring out the best in gem. So, they must be cut at the right angle and have a good polish. Also not having a crooked looking pavilion!
A tip on gemstone anatomy!
The culet is the small facet at the bottom of a diamond intended to prevent chipping and abrasion to the point. The culet size can affect face-up appearance of the gem.