Just What is Gemstone Luster?
The word is used all the time to describe gemstones, but what is luster? And why does it really matter?
First, let’s start with what it is. Luster has to do with the way a gemstone reflects light. There are a few things that can effect this. The surface polish of the stone, if it lets light in and causes it to glow, and how reflective the stone is, in itself.
When it comes to classifying raw gemstones, luster is as important as the other traits a stone has, such as clarity, hardness and cleavage.
Here are the categories that a gemstone can take on in their luster.
Adamantine – When you think of the amazing sparkle, glow and shine of a diamond, this is the luster you are seeing.
Dull or Earthy – As the names describe, these stones are very earthy looking, or dull, not reflecting light, and having an overall blah finish.
Greasy – The finish of these gemstones makes them look as if they are covered with a grease coating. Jadestone is a good example of this look, as is soapstone. Soapstone takes it to a whole new level because it also has a greasy feeling to the stone surface.
Metallic – The name says it all. The luster of this gem is very metallic looking, such as hematite or pyrite (fool’s gold).
Pearly – Think of the stone mica. It has a milky-pearly appearance on the surface. This is what a pearly luster appearance is. The stone exhibits that look of a pearl coating.
Resinous – Stones that look as if they could be resin, such as amber, are perfect representations of this luster classification.
Silky - This looks almost like the stone may have veins of silk fibers in it, when you look at stones like tiger’s eye you can see the smooth surface with the silky veins within the stone.
Vitreous – This is the most common of luster, describing any stone that has a finish that looks like glass.
Waxy – you’ve no doubt looked at a stone like turquoise and thought it really looks a lot like a ball of wax, that’s because it has a waxy luster.
If you’re looking at your aquamarines to check on their luster, generally aquamarines fit in the vitreous to resinous categories.
