Real of Fake? Identifying Genuine Black Diamonds
Black diamonds are rather distinctive gemstones, but they have a few convincing imposters. A gemologist with professional instruments can run tests to confirm a stone's identity without damaging your jewelry. .Aside from using a diamond tester (you can buy a portable one online starting at around $100), your options are more limited, but most minerals do have special characteristics that you can see and feel without any special equipment.
Here's a quick list of the stones and manmade substances with which they are most commonly confused and some tips for telling them apart!
Black Cubic Zirconia
The most fabulous of the fabulous fakes, cubic zirconia can be identified only with a thermal conductivity tester and by being observed through high-powered magnification.
Black Spinel / Synthetic Black Spinel
Though not as hard as diamonds, spinel is one of the better impostors. If you have access to a "black light", spinel (natural and synthetic) often fluoresces red, orange or pinkish under ultraviolet light, whereas a diamond will not.
A genuine diamond can scratch a spinel, however we most emphatically do NOT advise you to test your jewelry with your engagement ring! Thermal testing is one of the safest and easiest ways to uncover this diamond wannabe.
Often used in pave settings, as accent stones, or to frame colored gemstones, Marcasite has a distinctive metallic luster and the color normally has a slight yellowish/brownish tinge.
Black Glass ("French Jet")
"French Jet" was the name used for black glass - worn in Victorian times by those who couldn't afford genuine jet. Black glass is still used in costume jewelry today. Glass may be totally opaque (unlike an enhanced diamond). If it is transparent you may be able to see gas bubbles in it under magnification. There may also be seams around the sides of glass "stones."
"Alaskan Black Diamond" (Hematite)
Any confusion here is in name only. Hematite is a heavy, opaque, grayish-black mineral with a dull metallic luster. It looks a little bit like Marcasite (see above) but doesn't really resemble a diamond!
Natural vs Enhanced Diamonds
If you are certain your stone is a diamond, then the only question is whether the black color is natural or if it has been enhanced. To determine this, you need magnification and a strong source of light.
If the diamond has been enhanced through irradiation, strong light will pass through it and you will notice either an overall greenish or bluish cast, or glints of green or blue when viewed from certain angles..
One color treatment which is very hard to detect is when a very "included" white diamond is heated in a vacuum to the point where graphite forms inside of it. These stones can only be differentiated in a lab. However, this treatment is not common - nowadays, nearly all color enhancement is done through irradiation.
If the diamond is naturally black, you will observe a "salt and pepper" effect inside of it - alternating areas of black and white - when you examine it against the light at high magnification. There will be no hints of green or blue.
Gen quality natural black or gray diamonds are not common and command a high price. They are for the most part to be found only in high-end designer pieces. Unless you have been told otherwise by your jeweler, you can safely assume your the black diamonds in your jewelry have been color enhanced.
The following black stones are not intentionally used as substitutes for black diamonds and are less likely to be confused with them.
"Black Onyx" ("Black Chalcedony" - usually dyed gray onyx)
Usually used in beads or cabochons, the stone commonly called black onyx is massive and opaque, not crystalline.
We're including Jet in this list because it is a black stone once to make jewelry, however it would never make it as a convincing stand-in for a diamond. Jet is a very lightweight mineral with a dull, satiny sheen - it lacks the glossy surface of a polished diamond. You may find Jet in pieces from the 19th century, particularly in Victorian mourning jewelry. It is rarely (if ever) used today.
Black Tourmaline (Schorl)
Not often used for jewelry, black tourmaline is translucent to opaque. Tourmaline grows naturally in long crystals, making it more suited for being finished as emerald and oval cut stones. Testing for thermal conductivity will clear up any confusion.
When in doubt, asking a professional jeweler is the most reliable way to determine what stones are in your jewelry and whether your diamonds are real or not!
Attribution for Schorl and black diamond crystal photographs: Rob Lavinsky, iRocks.com – CC-BY-SA-3.0.
Author Mary G., AJP, is a GIA (Gemological Institute of America) alumni and an Accredited Jewelry Professional.