Lustre, which can also be spelt luster, is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word traces its origins back to the Latin word lux, meaning light and generally it still implies radiance, gloss or brilliance.
A broad range of terms are used to describe the lustre of minerals and there are no strict boundaries so the same mineral can often be described differently.
Some of the better known terms are:
Resinous - Amber is a resinous mineral. It has the appearance of resin, chewing gum or (smooth surfaced) plastic. Amber is a form of fossilized resin.
Dull - Although not a particularly enticing word, a gemstone which has a dull lustre is one which isn't obviously highly polished and clearly reflects light. An example would be meteorite.
Vitreous - Calcite, Quartz, Topaz, Beryl, Tourmaline and Fluorite are all vitreous minerals. This means they have the lustre of glass. This type of lustre is one of the most commonly seen and occurs in transparent and many translucent minerals.
Waxy - Unpolished Chalcedony and Jade both have a waxy lustre. A waxy lustre simply means a lustre which resembles wax.
Chatoyancy - Chatoyant minerals display bands or markings which appear to move as the specimen is moved and catches the light. Such minerals are composed of parallel fibers (or contain fibrous voids or inclusions), which reflect light into a direction perpendicular to their orientation, thus forming narrow bands of light. The most famous example is Tigers Eye but there are also plenty of other gemstones which can be chatoyant and Pietersite is one of the rarer ones.
Schiller - From the German for 'twinkle, this term is used to describe the metallic iridescence originating from below the surface of a gemstone that occurs as light is reflected between layers of minerals. It is most commonly seen in Moonstone and Labradorite and is also known as labradorescence.
| ← Louis Comfort Tiffany | Maasai → |
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