Minerals and light
Minerals and light
Take a mineral and hold it up to a light - what can you see? One of the first things you should notice is whether you can see through it or not.
Choose a thin section, an edge or corner. You should be able to judge whether your mineral is transparent, translucent, or opaque. This property is a useful tool to help you to identify your collection.
Most minerals are transparent (you can see right through them, like plain window glass), or translucent (more like frosted glass). Tiny bubbles of gas or other impurities trapped inside a crystal can make a transparent mineral look translucent. Metals like gold and silver, and some minerals containing metals, are opaque - you cannot see though them at all.
In the pictures below, the calcite is transparent, while the gypsum is translucent and the gold is opaque.
