Gemstones date back thousands of years. Earliest peoples appreciated gems for their brilliance and beauty, and early jewelers used gems to enhance their precious metal creations. Many stones had legends and powers associated with them, which added immeasurably to their value.
Today jewelers often refer to gemstones other than diamond as “colored stones.” They are either minerals or organic materials. Of all the minerals found on earth, about 20 are classified as mineral species gemstones, though other minerals are used in jewelry from time to time. Organic gemstones are those formed from a living substance, such as coral, amber and pearl.
Other colored gems were once referred to as “semiprecious,” a term that is misleading and isn’t used today by most jewelers. Now these are simply called “gemstones.”
Some gemstones have characteristics called phenomena that enhance their beauty and value.
Chatoyancy (Cat’s Eye) is the changeable, wavy, silky sheen shown by fibrous material and is seen in cat’s eye, chrysoberyl or tiger’s eye.
Asterism (Star) is a starlike effect caused by regularly arranged inclusions of minute size, as in star sapphire.
Change of Color occurs when a gem is one color by daylight and another by incandescent light, as is alexandrite.
Alexandrite: in daylight, bluish green
through slightly yellowish green;
under incandescent light, orangey red through purple/red