When light is reflected off the surface of a gemstone it is referred to as “lustre” (also spelt “luster”).
Different gemstones have different types of lustre and in gemmology there are several universally accepted terms to describe these appearances
Several transparent gemstones with a high refractive index are said to possess an adamantine lustre. The word is derived from “Adamas”, the Ancient Greek word for Diamond; a gemstone which displays a dazzling adamantine lustre.
Technically speaking, only those gemstones with a high refractive index tend to have an adamantine lustre. If you have invested in a portable refractometer you will be aware that the reading stops at around 1.85, therefore if you don’t get a reading whilst analysing a gemstone, and if it also has a fantastic lustre, then you have already started to dramatically narrow the range of possible gems that it might be.
Other gemstones that feature this captivating lustre include Zircon and Demantoid Garnet.
Gemstones with a high refractive index, but not quite that of Diamond, Zircon or Demantoid, are said to have a subadamantine lustre. These include some members of the Garnet family and fine examples of Sapphire.
When light is reflected off the surface of a gemstone it is referred to as “lustre” (also spelt “luster”).
Did you know?
In addition to being used to describe an optical effect, Adamantine is also the name of a gemstone which belongs to the Corundum family.
