1. "beautiful", that gorgeous crystal clear, sparkling gems, if not beauty can't be gems, this beauty or brilliant colors, or as transparent and clean, or with special optical effects (such as cat's eye, change color, luminous phenomena), or with special designs (such as Chrysanthemum stone, agate, jade plum, etc). 2. "a long time", that is, hard wear-resistant, capable of enduring due to the gem of high value, people would expect it to be durable, can preserve or even traditional items. 3. "rare", which yields less rare precious, rare emeralds in the world, the finest quality per carat (0.2 g) worth tens of thousands of dollars, and some very beautiful and can be resistant to "long" gemstones (Amethyst), since there are more production and exploitation easier, its price has been low. Some common rock, after pondering also features beautiful and durable, but gems cannot be a member of the family, and the reason is easy to get cheap.