Garnets are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives.
All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different species are pyrope, almandine, spessartine, grossular (varieties of which are hessonite or cinnamon-stone and tsavorite), uvarovite and andradite. The garnets make up two solid solution series: pyrope almandine-spessartine and uvarovite-grossular-andradite.
When thinking of garnet, most people think of red gemstones. Garnet most commonly occurs in red, and the origin of the name “garnet” lies in this deep red hue. The name “garnet” comes from the Medieval Latin word, “granatum”, which is an adjective meaning “dark-red”. It is thought that this adjective could have been extracted from the word “pomegranate”, due to the colour of the seed coats or shape of the seeds. However, the word could also have come from another Medieval Latin word; “granum”, referring to red dye. The use of red garnet dates back thousands of years, when it was used by Egyptian pharaohs for both decorative and ceremonial purposes. The ancient Romans also wore garnet rings and traded garnet gemstones. In ancient times, garnet and other red gemstones cut en cabochon were called “carbuncles”, which is not the prettiest of names because it was also used to define pus-filled boils.
The Latin word, “carbunculus” alludes to a burning piece of coal or ember. This may have been used to refer to garnet because of its bright colour. Large deposits of red garnet were discovered in Bohemia (Central Europe) around the 16th century, which became the focus of the jewellery industry in the area. Bohemian garnet from the Czech Republic continues to be mined today. Although red is the most commonly occurring colour, garnet occurs in almost every colour. One of the most recently discovered colours of garnet is the rare blue garnet, which was discovered in the late 1990s in Madagascar. It has since been found in other regions, such as the USA, Russia, Kenya, Tanzania and Turkey. Garnet is a gem group that occurs in over twenty varieties. Of these varieties, six main types are used as gems. These are pyrope, almandite, spessartite, grossularite, andradite and uvarovite.
Garnet can be identified by its occurrence in metamorphic rock, its hardness (6.5 – 7.5 on the Mohs scale), colour, refractive index and cubic crystal structure. However, the quickest way to identify garnet is with the use of strong neodymium magnets. Garnet is attracted to neodymium magnets because it contains high concentrations of iron and/or manganese.