The name garnet is derived from the Latin word granatus “grain,” referencing the pomegranate fruit which has red seeds similar in color, shape, and size to the garnet. The most common color of garnet is red but there are many other colors including, orange, yellow, green, pink, purple, brown, black, and colorless. Garnet is the traditional birthstone for January, and has been used for many thousands of years. References towards the stone can be found in both the Bible and the Koran. Garnet was also used in North, South, and Central America by Indian tribes who thought of it as sacred. Garnet is a semiprecious gemstone that is popular in jewelry
While there are many types of garnet, they have essentially the same isometric crystal structure varying in their physical properties and chemical composition. There are six common species of garnet based on their chemical composition which are; pyrope, almandine, spessartine, grossular, uvarovite, and andradite. From these six, two main groups are formed: pyralspite (pyrope, almandine, spessartine), and ugrandite (uvarovite, grossular, andradite). A natural garnet’s composition generally falls somewhere between the two main groups and are rarely if ever found precisely matching the pure species. A variety of garnet called mozambique is red to orange-red in color. Its chemical composition is a mixture between pyrope and almandine, averaging a 1:1 mixture respectively. Another variety using both pyrope and almandine is rhodolite, a rose-red to purple garnet with a composition mixture average of 2:1 respectively.
Grossular garnets that are brown, orange-red, or yellow-orange are known as hessonite. Rare forms of garnet such as tsavorite and demantoid occur when ions such as Cr3+, V3+ and Ti3+/4+ replace the common composition of the mineral. Color change garnet can also be found. This color change occurs when the stone is placed under fluorescent light versus incandescent light. The cause of the color change is impurities, in large amounts, of vanadium or chromium in malaia garnets.
Garnet deposits have been discovered in Africa, Argentina, Australia, Brazil, Canada, Finland, India, Madagascar, Myanmar (Burma), Russia, Scotland, Sri Lanka (Ceylon), Switzerland, Tanzania, and the United States (In the states of; Arizona, Colorado, Georgia, Idaho, New Hampshire, New Mexico, North Carolina, Pennsylvania, Utah, Virginia).
Properties, Treatments & Lab Created
Garnet is rated a 6.5 – 7.5 on the Mohs scale.
The only current garnet treatment known and used is on demantoid garnet. It is sometimes mildly heated to enhance the color.
Garnet is not currently made in laboratories, but there are simulants and cubic zirconias with similar color to garnet.