Lustre of Gemstones

The way light reflects on the outside of a gemstone is described as its lustre. This lustre will be affected if the stone has been polished, of course. Generally, there are nine descriptors of lustre – metallic, waxy, pearly, silky, vitreous, adamantine, resinous, greasy and dull. I won’t go through all of them but let’s look at some of the most important lustres.

The first is Adamantine: The word refers to diamonds, something that is hard, and reflecting brilliant light. It is derived from the Greek word ‘adamas’ meaning ‘unbreakable’.

Next is Vitreous: ‘Vitrum’ is the Latin for glass, so a gemstone with a vitreous lustre shines like glass. This is the most common lustre and includes emeralds, spinel, topaz, beryls, quartz and tourmalines.

Metallic lustre is where the gemstone shines like a metal. Pyrite, mascasite and haematite have metallic lustres.

A Waxy lustre is seen in gemstones such as turquoise, jade, chalcedony and opals.

And finally, a Resinous lustre, which is when the gem reflects light like resin, hardened tree sap. Amber is the classic example of a resinous lustre.