In the world of beautiful gemstones, there are two things that matter quite a bit: colors and sparkle. Garnets accomplish both of those better than many others.
The combination of color and sparkle from certain species of garnet earned them the names carbunculus in Latin and anthrakas in Greek in the Ancient World: both of which translate as “a burning ember.” Now, it’s fair to mention that those terms were applied with a broad brush to several types of red gem materials. But given the deep, smoldering orange-red of the most common gem varieties of garnet, it’s easy to understand why garnets were included in that grouping. In fact, garnets were once believed to shine so brightly that they glowed in the dark.
As to the colors of the garnet family, most people envision the dark, fiery reds that were so popular in Victorian Era jewels. But there is a lot more to it than that. The garnet group of minerals is divided into six species with varying chemical compositions that offer some visual effects many people don’t know garnets are capable of.
The six major species of garnet are pyrope, almandine, spessartine, uvarovite, grossular, and andradite. Each one has its own primary color, and some of the families intermingle to make colors that are greater than the sum of their parts.
While the British and the Bohemians (present day Czech Republic) favored the deep, sensual red of the pyrope and almandine species, the Ancient Greeks treasured a cinnamon brown variety of grossular garnet called hessonite.
But grossular garnet has more to it than that. “Grossular” comes from the Latin word for gooseberries, so grossular garnets are stereotypically gooseberry green. Grossular garnets actually occur in every color except blue. Some of the rarer examples are so-called raspberry garnets from Mexico and the extremely rare and truly colorless leuco garnets that gem collectors gobble up before most jewelers get a chance at them. And of course, there’s tsavorite: a grossular garnet found in Kenya that rivals emerald for its exceptional green.
Grossular isn’t the only garnet that does green, though. Uvarovite, the rarest of the garnet families, is colored green by its inherent chromium content. Few are the eyes that have a seen a faceted uvarovite gem because crystals are usually either too small or too opaque for faceting (or both). However, there are gorgeous druzy specimens from Russia and Finland that are suitable for use in jewelry and display a color that is adequately described as electric green.
The other green garnet is produced by the andradite family. Demantoid garnet is far and away the most valuable garnet out there. Like uvarovite, demantoid is colored green by chromium, which is also what colors the best emeralds. All andradite is known for its exceptional sparkle. Technically speaking, andradite garnets have the highest refractive index and dispersion values of all the garnets, and they actually rank in the top tiers of all gemstones in optical properties. Andradite also produces a fine yellow, a rusty red, and one of the rare, true black gems of the world.
The last garnet family is spessartine, named for the location of its discovery, the Spessart Mountains in what was once Bavaria. Spessartine only comes in one color: orange. There’s reddish orange; there’s yellowish orange; deep, dark orange, and bright, playful orange; but spessartine is only orange. It’s colored by the manganese content of its chemical composition. It has exceptional sparkle and is a favorite of custom gem cutters. Spessartine garnet is found in several locations around the world, most notably Namibia.
But garnets don’t stop there.
Chemical mixtures of pyrope and almandine can form some lovely purple garnets and pink garnets. Rare color-change garnets that show blue-to-purple and purple-to-pink color changes are various mixtures of pyrope and spessartine, with a little bit of grossular or almandine thrown in. Garnets from Mali are a mix of andradite and spessartine and offer dazzling yellows in all shades. So-called malaya, or “outcast” garnets from Tanzania display many shades of pink, red, orange, and purple; they are a mixture of spessartine and pyrope. Then there are iridescent garnets from Mexico and Japan, which are mixtures of andradite and grossular.
Care and Cleaning
Garnets are suitable for mounting in all kinds of jewelry, although there is some varying hardness to consider between the species. Pyrope, almandine, and spessartine all tend to be slightly harder (7-7.5 Mohs Hardness) than uvarovite, grossular, and andradite (6.5-7.5 Mohs Hardness).
Of the six families, uvarovite is the least wearable in jewelry because of its druzy formation. The crystals can chip and flake off, or the whole piece can break when struck, so rings and bracelets are not the best choice unless they’re worn sparingly. But uvarovite definitely makes for some striking earrings, pendants, and brooches.
Faceted gems from the other five families are fairly resilient and great for rings, pendants, earrings, whatever. Pyrope and almandine (the common reds and pinks) and spessartine are all pretty hard-wearing and don’t chip or break too easily. Andradite and grossular are slightly more brittle, and gems worn in everyday rings will show abrasions of the facet junctions sooner than most people might like.
All of the garnet species are stable enough for ultrasonic cleaning for stones that are not fracture-filled or highly included.
Steam cleaning isn’t really recommended for garnets, but it still happens every single day. Warm water, mild dish detergent, and a soft toothbrush are a great way to clean all garnet jewelry if you can’t make it in to your local independent jeweler.
It’s worth noting that all garnets are attacked by hydrofluoric acid, which is used for glass etching, and is a common ingredient in household rust and water-spot removers. Be sure to remove your garnet jewelry before going after those hard water stains or the rust on the chrome hubcaps of your ’76 Monte Carlo.
Garnets are one of the few gemstones out there that are rarely, if ever, enhanced. Most don’t respond favorably (if at all) to heating or irradiation. The exception to that is demantoid, but not all demantoid responds to heat treatment. Fracture-filling is the next most common treatment of garnets, and that’s still kind of rare, as well as pretty easy to spot.
You can mostly assume that any garnets you’re looking at are natural and unenhanced.
So, suppose you’re a January baby, and you, for whatever reason, have never been fond of your birthstone. Might we humbly suggest it’s because you may not have known about the vast variety available to you? There’s an awful lot to see in the world of garnets, and there isn’t a speck of it that isn’t pretty.