![](https://www.langantiques.com/university/wp-content/uploads/2023/01/This-Diamond-Exhibits-an-Adamantine-Luster.-The-Term-can-also-Refer-to-a-Diamonds-Extreme-Hardness..jpg)
![Zircon, While Highly Dispersive, has a Subadamantine Luster.](https://www.langantiques.com/university/wp-content/uploads/2023/01/Zircon-While-Highly-Dispersive-has-a-Subadamantine-Luster..jpg)
Adamantine is the term used to describe the luster exhibited by diamonds and gems with a Refractive Index of 1.9 – 2.5. The root word adamant derives from the Greek word adamastos which means untameable. Throughout history the word adamant has been used in reference to anything that was composed of a particularly hard material, diamond or otherwise.
Subadamantine luster is slightly less than that of a diamond. Example: Zircon.
![](https://www.langantiques.com/university/wp-content/uploads/2023/01/This-Diamond-Exhibits-an-Adamantine-Luster.-The-Term-can-also-Refer-to-a-Diamonds-Extreme-Hardness..jpg)
![Zircon, While Highly Dispersive, has a Subadamantine Luster.](https://www.langantiques.com/university/wp-content/uploads/2023/01/Zircon-While-Highly-Dispersive-has-a-Subadamantine-Luster..jpg)