Specific gravity


A mineral's specific gravity is the ratio of its mass to the mass of an equal volume of water. For example, magnetite has a specific gravity value of 5.2, meaning 1cm3 of magnetite will be 5.2 times as heavy as 1cm3 of water.


Although this property can be precisely measured, it is often tested by simply hefting the specimen in the hand. Estimating specific gravity in this way is a useful skill to develop, but care must be taken to allow for the size of the specimen.


Light, average or heavy are generally applied as relative measures of specific gravity, with a value of 2.7 being considered average, e.g. quartz or calcite.