Black Tourmaline, also known as Schorl, is a distinctive gemstone loved for its deep black colour.
However, telling genuine black tourmaline apart from its imitations or similar-looking gemstones can sometimes be a challenge if you don't know what to look for.
In this guide, you'll know the practical steps that help you identify real black tourmaline, so that you can be more confident next time you come across it.
Black Tourmaline Appearance
Colour
Genuine black tourmaline should display a deep black color, although it can sometimes appear dark brown under bright light.
Crystal Structure
Black tourmaline crystals are prismatic, often with several facets leading to a pointed termination. The flat sides of the crystal may exhibit striations or lines running parallel to the crystal's vertical axis.
Striations
Look for prominent vertical striations, ridges, or furrows along the length of the crystal. These striations are usually parallel and consistent, which is characteristic of tourmaline. Here is an example:
Terminations
The terminations or ends of the crystals are also indicative; tourmaline crystals often have a rounded or pyramidal termination.
Transparency
Black Tourmaline is always opaque with a vitreous lustre, giving it a glass-like appearance.
How To Tell If A Cut Or Polished Black Tourmaline Is Real
An unpolished mineral specimen of black tourmaline is relatively easy to determine the authenticity thanks to its unique appearance, but when the gemstone is cut or polished, it could be harder to tell it apart from similar looking black gemstones like onyx or obsidian.
Hardness
Black tourmaline has a hardness of 7-7.5 on the Mohs scale. You could conduct a scratch test on a hidden part of the stone if you have the tools, like near the hole of the bead or the back side of the pendant.
Weight
Black tourmaline is relatively heavy due to the presence of iron. It has a specific gravity of about 3.15, while other similar looking gemstones like onyx (Specific gravity of 2.7) or obsidian (specific gravity of 2.4) are lighter in weight. However, be careful of the even heavier gem of spinel with a specific gravity of 3.6, but spinel is usually more expensive than black tourmaline.
Appearance
Check for a consistent black color throughout the bead. The bead should also have a glassy lustre. Some small inclusions or imperfections may be visible upon close inspection.
Professional Assessment
If in doubt, a professional evaluation from a reputable jeweler or gemologist is the most reliable method to determine the identity of the stone.
