Spessartite, Hessonite, Tsavorite, Demantoid, Rhodolite

The garnet family of gemstones is quite extensive with over twenty species. Of these, only five are used for gemstones; spessartite, grossularite, pyrope, andradite, and almandite. These five species also have many sub-varieties due to the combination of two or more garnet species forming together. Colors of reds, greens, oranges, and virtually all colors except blue can  be found as garnets. While the chemical composition of these minerals varies, they all have the same cubic crystal structure and  are singly refractive.

Spessartite, also known as mandarin garnet, is a rare and beautiful gemstone with colors ranging from an intense orange to reddish or brownish orange. This gem is mined in Sri Lanka, Madagascar, Namibia, Zambia, Brazil, Myanmar, and most recently in Nigeria. Larger pieces of this beautiful gem are becoming increasingly scarce.

                                                          
Hessonite is a brownish yellow to brownish orange mineral which is  a form of grossularite garnet.  This gem is very appealing to the naked eye and makes beautiful jewelry.  Sri Lanka is the primary source for the rough material.

Tsavorite, a green form of grossularite, is a rare and highly prized gemstone. Most of the rough material is highly included so most of the clean cut gems weigh less than one carat. Larger stones command very high prices. Only the most saturated green stones are called Tsavorite. Gems with lower saturation and light tones are sold as green grossularite. Most tsavorite is found in Africa and Madagascar.

Demantoid  is a variety of andradite. It is another rare gem with colors ranging from yellow-brown  to intense greens. Some demantoid garnets are found with an unique inclusion called a horsetail. It appears as tiny mineral fibers inside the gemstone radiating from the center of the inclusion outward in a starburst fashion. Gems with this inclusion are highly prized by collectors. Most of the rough material comes from Russia and Namibia. 

Rhodolite, a mixture of pyrope and almandite, is the most valuable of the red garnets. The term rhodolite is usually given to garnets that contain some purple. Colors range from dark purple-red to light red-purple. Much of the material is free of inclusions and is ideal for jewelry. The major sources for rhodolite include Africa, Sri Lanka, and Madagascar.

Red Garnets are the most common garnets found in jewelry. Most of these are made  of pyrope or  almandite or a combination of the two. These four garnets shown, have refractive indexes ranging from 1.74 (pyrope) to 1.79 (almandite). They all look about the same and most of them are relatively dark. The cost of these garnets is quite low compared to most gems so the exact makeup is not a concern. They are usually just sold as red garnets.