Garnet (Molecule of the Month for March 1997)
The garnets comprise a family of complex silicates with widely varying chemical composition but similar structures. While everyone is familiar with dark brownish or purplish red garnets, many are unaware that garnets can occur in almost any color except blue (although there have been some recent reports of some color change garnets that are predominantly blue). Slight variations in chemical composition define the placement of a garnet within the family.
There are garnets that change color in different light, translucent green garnets that look like jade, garnets with stars, garnets that have been mined for thousands of years and garnets that were just discovered in the last decade.
The name garnet probably comes from pomegranate. Many ancient pieces of garnet jewelry are studded with tiny red stones that do look a lot like a cluster of pomegranate seeds! Jewelry set with garnets from Czechoslovakia was extremely popular in the nineteenth century and Bohemian garnet jewelry is still popular today, although today the garnets are mined elsewhere. When you say garnet, most people think automatically of small dark red gemstones, even though this is only one corner of the world of garnets. In fact the word brilliance is probably derived from the ancient greek word for beryl, berullos, which means crystal.
Morganite is probably the most popular of the other beryls. It has a pastel pink to peach or lavender which is similar in intensity to the blue of aquamarine. It was first discovered in California in the Pala pegmatites. It was also discovered in 1908 in Madagascar. There are also deposits in Brazil, Mozambique, Namibia, Afghanistan, and Russia. However, morganite is relatively rare, which stands in the way of it becoming a jewelry stone. The largest faceted morganite is a 598.70-carat cushion-shape from Madagascar in the collection of the British Museum.
Heliodor, or golden beryl, is named after the greek words for sun helios and gift doron. The sunny yellow color of this beryl lives up to its name. Heliodor was discovered in Namibia in 1910 in a pegmatite that also produced aquamarine, which is also colored by iron. Heliodore is also found in Brazil and Madagascar. The largest faceted heliodor, 2,054 carats, is on display at the Smithsonian Institution in Washington D.C.
Garnets have long been carried by travellers to protect against accidents far from home. In ancient Asia and the American Southwest, garnets were used as bullets because the glowing red color was said to increase the ferocity of a wound. Garnets in legend light up the night and protect their owners from nightmares. Noah used a garnet lantern to navigate the Ark at night. The ancient world is full of praise for the carbuncle, the glowing red coal of a gemstone we now now as garnet.
Garnet is the birthstone for January, which means that January babies have a lot of choices! Varieties available, some mineral differences and some color descriptions, include rhodolite, malaya, demantoid, grossular, hessonite, spessartite, hessonite, almandine, mandarin, and combinations beteen these varieties.
One of the most popular is rhodolite garnet,which ranges from pink to purplish red in color and is mined in Africa, India, and Sri Lanka. Tsavorite garnet is a bright yellow green to grass green, and is mined in Tanzania and Kenya. Legendary demantoid garnet combines a bright green with dazzling brilliance that won over the Tsars of Russia, who used it lavishly. Unfortunately demantoid garnet was only ever available in small sizes and is extremely rare today.
Malaya garnet, another popular mixed variety, ranges from orange to gold and is mined in Tanzania and Kenya. Pyrope garnet is a very saturated red: beautiful small pyrope garnets found in Arizona are called anthill garnet because they are mined by ants, who carry them up when they are excavating their anthills.
One garnet growing in popularity is a newly discovered garnet from Namibia, which is a bright orange spessartite, is called mandarin garnet because its color is a true orange. Hessonite and Spessarite garnets mostly come in golds and oranges and browns that are sometimes called cinnamon garnets. Grossular, the variety of garnets that gives us tsavorite, also is available in pale pinks and greens and yellows.
Garnets are fairly hard and durable gemstones that are ideal for jewelry use, except for demantoid, which is softer and requires more protection.
Formal Chemical Name (IUPAC)
Update by Karl Harrison
(Molecule of the Month for March 1997 )