Lustre

Definition

The quality and intensity of light reflected from the surface of a mineral. This property must be observed first-hand and cannot be demonstrated in a photograph.

Terminology

Metallic - strong reflection, shines like metal, may be very shiny (like a chrome car part) or less shiny (like the surface of a broken piece of iron);
Vitreous - glassy, bright (shines like glass);
Resinous - a resin-like shine (resembling amber for example);
Greasy - a dull sheen, has the appearance of being coated with an oily substance;
Pearly - a whitish iridescence (resembling pearl for example);
Silky - a sheen like that of a fibrous material, e.g. silk;
Adamantine - a brilliant lustre such as that of diamond;
Earthy - like the surface of unglazed pottery