The luster of a mineral is best observed on a surface that is free of moisture, dirt, tarnish, and abrasion. Geologists in the field usually carry a rock hammer to break rocks so that their true luster and color can be observed. Breakage is usually not necessary when observing the luster of cleaned and cared-for specimens in a laboratory or classroom.

Luster is best observed under direct illumination. That allows the light that strikes the specimen to reflect to the eye of the observer. Proper examination includes moving the specimen (or the light source, or the head of the observer) through a range of angles to observe the full character of the luster.