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The Colours of Garnet, Part 1: What is Garnet?

By Yaĝé Enigmus

 

For most people, the word “garnet” is synonymous with the colour red. In truth, red is merely one colour that garnet gemstones are known for. Now the contemporary Western birthstone for the month of January, the term “garnet” is the name for a group of related minerals, rather than a single stone. These minerals occur in a myriad of colours other than red, proving a vast array of gemstones from which to choose.

Garnet gemstones of various hues

Garnet gemstones of various hues. Image: GIA

 

Red garnets are the most plentiful garnet gemstone and have the longest history of use; in the ancient world, dark red gemstones were known as “carbuncle” with this term being used to refer to garnet in the majority of cases. Carbuncle gemstones have been found in ancient Egyptian tombs, and legend has it that carbuncle was one of the precious gemstones given to King Solomon by God in the Old Testament. The contemporary English word “garnet” is thought to be derived from the Old English word for dark red, “gernet”, which itself is linked to the Old French “grenate”, the same root for the contemporary French word for pomegranate. Cinnamon-coloured Hessonite garnets were also known in the ancient world, particularly in South Asia, and these were called by the name “gomed”, but such stones did not become well known in the west until more recent times.

A ring featuring a faceted red garnet gemstone
A ring featuring a faceted red garnet gemstone. Image: GIA/Tino Hammid


Following advances in the science of mineralogy, it was discovered that red garnets would vary substantially in chemical composition and that the gomed stones of South Asia were also chemically similar to red garnets. These stones were related by shared components of their chemical structures, and this became the basis for characterizing what is now known as the “garnet group”. Members of the garnet group all have a chemical makeup that follows the pattern X3Z2(TO4)3 where the X site is occupied by a divalent element, the Z site is occupied by a trivalent element, and the T site is most commonly occupied by silicon (Si), but arsenic (As), vanadium (V), aluminum (Al), tellurium (Te), or iron (Fe) may also occupy this site; today there are over twenty species of garnet that have been documented, but only six are utilized in jewellery, with all six of these species possessing chemical formulas that are based around silicon - i.e. X3Z2(SiO4)3 - and falling into the mineral category of “nesosilicates”. 

Garnet Species

Many garnet minerals occur as multiple gemstone varieties; Image: GIA

Every gem species of garnet has slightly different colour capabilities, with the six major garnet minerals as a whole exhibiting nearly every colour in the rainbow. These six minerals are pyrope garnet, almandine garnet, spessartine garnet, uvarovite garnet, grossular garnet, and andradite garnet. Red garnets can be one of multiple different garnet minerals and in some cases may even be a mixture of multiple species, but typically these stones are almandine garnet and/or pyrope garnet; the other four major garnet species cover a wide variety of hues, with some garnets even being colourless or appearing to change colour in different lighting conditions.

An antique hairpin featuring rose-cut pyrope garnet gemstones
An antique hairpin featuring rose-cut pyrope garnet gemstones. Image: GIA/ Chip Clark


In the next installment of this series, learn more about pyrope garnet, almandine garnet, and spessartine garnet.

 

Here are some beautiful pieces of jewellery from Skyjems, featuring red garnets!

Rhodolite Garnet Stacker Ring set in 14kt Yellow Gold
Almandine Garnet Earrings set in 14kt White Gold
Almandine Garnet Earrings set in 14kt White Gold

 


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