Turquoise is an opaque, blue-to-green mineral that is a hydrous phosphate of copper and aluminum. It is rare and valuable in finer grades and been prized as a gem and ornamental stone for thousands of years owing to its unique hue. In recent times turquoise, like most other opaque gems, has been devalued by the introduction of treatments, imitations, and synthetics onto the market, some difficult to detect even by experts. The substance has been known by many names, but the word turquoise was derived around 16th century from the French language either from the word for Turkish or dark-blue stone. It does not occur in Turkey but it traded at Turkish bazaars to Venetian merchants who brought it to Europe. The color, however, has been employed extensively in the decorative tiles adorning Turkish places of worship and homes for hundreds of years, beginning with the Seljuk, or was derived from the color of the Mediterranean Sea on the southern Turkish coast and the association quite possibly has caused the name to take root.

Rings

A finger ring is a circular band worn as a type of ornamental jewelry around a finger; it is the most common current meaning of the word ring. Other types of metal bands worn as ornaments called rings, such as arm rings and neck rings. Rings worn by both men and women and can be of any quality. Various ring shapes and styles exist. The following are but a few. Flat wedding bands are the simplest form of ring. A flat wedding band consists of a strip of metal bent around into a loop and joined where the ends meet. Half-round rings, also called D-shape rings, are flat wedding bands filed half-round on the outside. Sleeve rings are rings that consist of a thin inner ring or sleeve, with several other rings stacked onto it to form one solid ring. Either the rings soldered onto the sleeve or the ends of the sleeve can be upset to keep them all together. A little of both can also be done. Solitaire rings are rings with a single large stone as a centerpiece, usually a diamond. Eternity rings are rings with stones, usually diamonds, of the same cut and size, set in one row all around the ring. The stones are usually round or square, and the setting is usually either claws or a channel setting. When the stones do not continue around the entire ring, but stop halfway around the finger, it is a half-eternity ring. Trinity rings or Trilogy Rings are three rings worn at one time. Cluster rings are rings with a group of stones in a cluster setting, forming the focal point of the ring. The cluster setting usually consists of one large stone in the center surrounded with several smaller stones. Tension Rings are a type of ring in which a single gemstone is held in place by pressure rather than prongs, a bezel or other mounting. The metal setting is actually spring-loaded to exert pressure onto the gemstone. In the United States and Canada, ring sizes specified using a numerical scale, with quarter and half sizes. An increase of a full size is an increase of 0.032 inch in diameter, or roughly 1/10 inch in inside circumference. Generally, sizes in quarters and halves will not relate conventionally to anything on any known ruler. On one finger alone, a person may vary more than a whole ring size- depending on time of day, work performed, and other swelling-inducing activities/conditions. Therefore, in most cases quarter-sizes are meaningless unless one needs precise accuracy with a particular ring.