Well formed crystals
A careful look at a well-formed crystal with many faces gives us some idea of the complexity of the laws of crystal symmetry, which are among the features distinguishing crystals from living organisms. Another difference between the members of the mineral kingdom and living things is the range in size of members of any one species. The adult size of any member of a species of animal or plant is confined to fairly narrow limits, but there is practically no limit to the possible size of a crystal of any one mineral. This is governed by the supply of liquid from which the mineral crystallised, the temperature and pressure prevailing at the time, and, of course, the space available. The size of single crystals of a given mineral may vary from a mere fraction of a millimetre to enormous masses weighing more than a hundred tons.