central heating - a heating system in which air or water is heated at a central furnace and sent through the building via vents or pipes and radiators
exists and is an alternate of . Five physical characteristics of a mineral are: hardness, luster, diaphaneity, colour, and streak.
There are some substances, like opal, which have the appearance of a mineral but lack any definite internal structure, are sometimes called mineraloids. Lutgens and Tarbuck give the following list of essential characteristics of a mineral: 1  It must occur naturally.