Garnet

For most people outside the gemstone and jewelry trade, Garnet is just the name of a low priced red gemstone assigned as the January birthstone and and associated with the 2nd anniversary of marriage. In fact, Garnet is not a single mineral, but a family of at least six related and cross-mixed varieties available in almost every color of the spectrum and in a price range for every budget.

The family name Garnet comes from the Latin word "Garanatus", which means "seedlike" in reference to a pomegranate seed size and color. But to add more confusion, garnets are usually called by their trade names that represent either a very specific color, like Mandarin Garnet and Color Change Garnet, or a place where that garnet was discovered and mined, like Bohemian garnet, Tsavorite or Mozambique Garnet.
Garnet is one the few gemstones that cannot be treated and as a result has enjoyed a huge resurgence of popularity. As gemologists and collectors have embraced the beauty and rarity of these gemstones, prices for some of the colors have doubled or even tripled in recent years. It is not because treatments have not been tried, it´s just that heat or radiation or any of the other gemstone enhancement techniques have not been effective for garnets. And, because so many of the stones are relatively clean, they also do not need to be oiled or infused with clarity enhancers to improve their appearance.
All species of garnets are related by a range of physical properties and crystal forms although they may differ in chemical composition. Garnets crystallize in the cubic or isometric system and are singly refractive. They may in some cases display excellent dodecahedral or trapezohedral crystallization but most garnets are found as water worn pebbles or irregular fragments depending on the nature of their geological history. Garnets do not show cleavage, so when they fracture under stress, sharp irregular pieces are formed.
With a hardness of 6.5 to 7.5, and no cleavage, garnets are relatively tough gemstones that can be used as a centers or accents in any kind of jewelry. They are not heat sensitive. Gem quality stones are normally faceted and sometimes cut en cabochon. Asterism is rare but 4 rayed stars are found in some areas. All species of garnet have been used as gemstones and red garnets have been among the most commonly used gemstones since the beginning of civilization.
Garnet varieties are found in almost every color of the spectrum, but the rarest of these are the blue color changing garnets discovered recently in Madagascar and the green demantoid garnets discovered in Russia more than a century ago. And, although garnets are found on every continent, Africa is and will most probably continue to be the most important and diverse source for the best garnets of any color.
Fonte: Seleções