Diamond Identification Made Simple

Diamond is perhaps one of the easiest stone to identify.  There are many physical properties of diamonds that are unique by itself and these characteristics are not found in other colored stones.

Below are some ‘quick and dirty’ methods for identification of a diamond. Some of these tests are conclusive, others are more collaborative. It may tell you that a stone is not diamond, but you cannot confirm that the subject stone you are testing is a diamond, until further tests are carried out to confirm its identity.

Care must be taken that a synthetic diamond will also pass these tests.  Synthetic diamonds have the same properties as natural diamonds, except that they are man-made and grown in laboratories using various high technological methods.

Simple Steps

The Refractive Index of diamond is 2.417.  This is perhaps one of the highest RI found among gemstones.  But RI is never used for identification of diamond as the normal gemological laboratory Refractometer does not read beyond 1.80.

As a diamond has a very high RI, light rays that enter a diamond is refracted and reflected from within like a prism and the prismatic effects bend the rays at such impossible angle that you cannot read any text through a diamond.  

Hence, when you place a Round Brilliant Cut Diamond face-down onto a pencil drawn line or some typed words, there is a no see-through effect, that is, you cannot see the line or the words inside the diamond.  With other gemstones with a much lower RI, you will be able to read the wordings through the pavilion facets.

The girdle of a diamond is the thin perimeter on the circumference of the stone. When seen from a profile view, this diameter is the widest part of a diamond dividing the crown above from the pavilion below.

There are 3 types of girdle finishing on a diamond, that is, faceted, polished and bruted. A bruted girdle has a grainy and frosted appearance, as this type of brutting is achieved when two rough diamonds are grinded against each other. Previously, a bruted finish on the girdle was very common as this is a direct means of identifying a diamond. Hence, if you view a diamond on the girdle and it is frosted, you can be assured that the subject stone is a diamond.

Currently, most diamonds have faceted girdle as it is more transparent and it gives the diamond a wholesome look.

As diamond is the hardest mineral, hence, it has very sharp facet junctions.  If you see a lot of tiny fractures along the faceted junctions of a colorless stone, it is not likely a diamond.

The way a diamond or a colored stone fractures can also reveal a lot of information on the identity of the stone.  Diamond is the only stone that has a step-like fracture, as compared to glass where the fracture is conchoidal, meaning curve-like. Other color gemstones fractures in different way, unlike that of a diamond. If you have a cut diamond and there is a sizeable fracture on it, use a loupe to view the fracture surface carefully.  It is likely that you will see the step-like fracture. Alas, when you see a fracture stone, most likely you will not buy the diamond.

Most diamonds have tiny root-like tendrils protruding perpendicular to the girdle which are called beardings.  However, in very well cut diamonds you may not find any of these beardings. Bearding can affect both the clarity grade and the polish grade of a diamond.  If there are beardings on the girdle of a diamond, then the specimen stone is a diamond.

Trigons are minute triangle-like crystal indentations on a rough diamond.  Most cutters will try to retain these trigons on the side of the girdle.  But these are rare and the price of a particular diamond with trigons on the girdle have a very high premium.

And of course a diamond tester is the easiest way to identify a diamond.  Diamond is a very good conductor of heat.  When a diamond tester is switched on, the probe will heat up and when it touches a diamond the heat is conducted away quickly which will be indicated with a small high pitched sound and normally a green indicator will alight.  Other stones will not respond to this test. 

However, Moissanite, will respond positively to this test, that is, on a diamond tester, it will show a green light. Moissanite is a naturally occurring crystalline silicon carbide. Its hardness is 9.25 on the Mohs scale and it has a higher refractive index than diamond, hence, its sparkle and brilliance are even better. However, Moissanite is Double Refractive. You have to carry out further tests to separate between a diamond and a Moissanite.

Good luck

Photo credit: gia.edu, estatediamondjewelry.com, perfect-ring-blog.blogspot.com, capetowndiamondmuseum.org, beyond4cs.com, dcla.com.au, imgur.com, geology.com, bitcoinist.com, brilliance.com


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