This is the minerals specific gravity . Water has a specific gravity of 1. Heavier' minerals like gold and galena have a higher specific gravity than 'lighter' minerals like quartz. Finally, many minerals have unique or special properties that make their identification easy. Halite has a salty taste while few other minerals have any taste at all.
Most clay minerals give off an 'earthy' smell when wet.
Magnetite is so named because it is ferromagnetic, giving off a magnetic field. When a piece of clear calcite is placed over an image on paper, it creates two images slightly offset from each other, called a double refraction . Some minerals will fluoresce , or glow, when an ultraviolet light is shown upon them. Minerals can be identified with several different diagnostic tools based on the physical properties of the mineral. These physical properties make identification of a mineral fairly easy when used in conjunction with a mineral identification key.