Some minerals are gems and some gems are minerals, but not all minerals are gems nor are all gems minerals. To be a gem, an object must display an inherent attractiveness (color, sparkle, or other optical property) and must be able to withstand the physical abuse that frequently accompanies treatment as a gem or piece of jewelry. Some of the popular "precious" gems such as diamond, ruby, emerald, and sapphire are minerals, too, because they are inorganic and naturally formed. Some other gems such as amber, pearl, and coral are not minerals due to their organic origin. Many minerals are not gems because they lack the esthetic appeal that a gem requires. Most minerals are, in fact, fairly plain from the standpoint of visual attractiveness. Other minerals do not have the stability or ruggedness to remain intact very long in jewelry. This has not stopped some attractive but fragile minerals from being fashioned into cut gems as a novelty.