The density, or specific gravity, of a substance is a measure of how much matter is packed into a certain space. It is the ratio of the mass of a substance relative to the mass of an equal volume of water. A mineral with a density of 2 is twice as heavy as water of the same volume. Minerals with low densities that feel “light” include graphite, talc, gypsum, halite, and quartz. Moderately dense minerals that feel a “little heavy” include cassiterite, crocoite, cuprite, mimetite, pyromorphite, vanadinite, and wulfenite. Very dense minerals that feel “quite heavy” include bismuth, gold, silver, platinum, and sperrylite.
All specimens from the David J. Eicher Mineral Collection; images © David J. Eicher