Garnet: A Diverse Group of Gemstones

History

Garnets have a long and storied past, with evidence of their use dating back to the Nile Delta in 3100 BC. Egyptian artisans crafted garnet into beads and jewellery. The name "garnet" comes from the Greek word "granatum", which reminded the ancients of the ruby-red seeds of the pomegranate. In earlier times, garnets were thought to light up the night, protect against nightmares, and safeguard travellers on their journeys. Today, garnets are admired globally for their vibrant colours and brilliance, gracing a wide variety of jewellery. Garnets are the birthstone for January and the gem for the second wedding anniversary.

Mineral Origins

Garnets are not a single mineral but rather a group of closely related minerals. These minerals include almandine, pyrope, grossular, spessartite, andradite, and uvarovite. Garnets are found in almost every corner of the earth, with specific colour variations depending on the region. The most common type is the red garnet, often only a few dollars to about one hundred dollars per carat, but they are also found in many other colours. Spessartine and hessonite garnets, which are orange and brown, are sourced from Namibia and Sri Lanka. The vibrant green demantoid garnet was first discovered in Russia's Ural Mountains. Tsavorite, a grass-green grossular garnet, is mined in East Africa.

The 4 C's

Like other gemstones, the quality of a garnet is assessed using the 4 Cs: colour, clarity, carat, and cut.

Colour

Garnets come in a wide array of colours, including red, orange, yellow, green, pink, purple, and even black and colourless. Red garnets, often a blend of pyrope and almandine, are the most common. Orange garnets, such as spessartites, especially the mandarin variety, are highly sought after. Green garnets, including demantoid and tsavorite, are rare and prized. The finest can rival sapphire or ruby in price, reaching thousands of dollars per carat. Tsavorite often shows emerald hues, while demantoid has a high dispersion but often exhibits undesirable yellow hues. Some garnets exhibit colour change properties, appearing one colour in daylight and another in artificial light. Colour is generally the most important quality factor for garnets.

Clarity

The clarity of a garnet depends on the specific type. Red garnets, such as almandine, pyrope, and rhodolite, are typically eye-clean, meaning they don't have visible inclusions. Orange garnets, like spessartine and hessonite, often have visible inclusions. Demantoid garnets frequently contain "horsetail" inclusions, which are considered beautiful and unique. Some garnets may also have inclusions that form a cat's eye or star effect, but these are very rare.

Carat

Garnets come in various sizes. Some varieties, such as demantoid and tsavorite, are rare in larger sizes, leading to a significant price increase per carat. Almandine garnets, on the other hand, are common in larger sizes, and their price per carat does not increase dramatically with size. Uvarovite is also extremely rare in facetable sizes.

Cut

Many garnets are cut into standard shapes and sizes for easy setting in jewellery. More expensive garnets, like tsavorite, are cut to retain more of their weight from the rough. The cut is very important to ensure the stone has brilliance, reflecting light evenly across the entire gem. Andradite garnets may be cut to feature their horsetail inclusions, while cleaner stones will be cut to showcase their dispersion.

Be Aware Of

Enhancements

Garnet enhancements and treatments are not common, and few garnets benefit from such processes. Most red garnets are rich in iron and can develop a metallic crust after heat treatment, although this is not usually desired by collectors. Demantoid garnets sometimes undergo a low-temperature heat treatment to reduce brown hues. This treatment is undetectable and creates a stable colour.

Simulants

Some synthetic gemstones are used to imitate garnets, but this is rare as many garnets are affordable. Colour-change glass can be used to simulate colour-change garnets. An unscrupulous dealer was once found to have sold colour change glass as natural garnet.

Synthetics

Synthetic garnets, such as yttrium aluminium garnet (YAG) and gadolinium gallium garnet (GGG), are often used as simulants for other gemstones. YAG is a poor substitute for diamond due to its low refractive index (RI), while GGG has a higher RI and makes a better diamond simulant. However, cubic zirconia (CZ) has largely replaced GGG as a diamond look-alike due to its lower cost.

Final Thoughts

Buying Tips

When buying garnets, it is best to see a variety of them to appreciate their wide range of colours. Consider unusual colours, as they can offer good value. Do not compromise on the cut, as this affects the brilliance of the gem. If you are making a significant purchase, consider getting a lab report.

Jewellery Care

Garnets range in hardness from 6.5 to 7.5, making them generally easy to care for. Stones with a hardness of 7 or higher are suitable for daily wear, as they are not easily scratched by household dust. Those with a hardness below 7 are more susceptible to scratching and are not recommended for everyday wear. To clean garnet jewellery, use warm, soapy water and a soft brush. Do not leave the jewellery submerged in water for longer than overnight.

Sources

Cited gemological sources
Authority	Title	URL
GIA	Gemological Institute of America, Garnet encyclopedia + quality factors	gia.edu/garnet
IGS	International Gem Society, Garnet buying guide + value, price, and jewelry information	gemsociety.org/article/garnet-jewelry-and-gemstone-information
AGTA	American Gem Trade Association, Garnet (January birthstone) reference	agta.org/gemstones/garnet

Frequently asked questions

What is rhodolite garnet?

Rhodolite is a natural blend of pyrope and almandine, prized for a clean raspberry to purplish-red color that is brighter and less brownish than ordinary red garnet. It is typically eye-clean and untreated, and it offers strong color for a moderate price, which makes it one of the most popular garnets for jewelry.

Are all garnets red?

No, and the assumption costs buyers money. Garnet is a group of related species spanning red, orange, yellow, green, purple, and colour-change material. Green demantoid and tsavorite are among the most valuable coloured stones on the market and sell for many multiples of red almandine.

Do color-change garnets really exist?

Yes, and they are among the rarest garnets. A color-change garnet can look blue-green or grey-green in daylight and shift to red, pink, or purple under warm indoor light. The effect comes from how the stone responds to different light sources. Strong, clean color-change stones are scarce and can be quite valuable.

How can I tell if garnet is real?

Garnet is singly refractive and reasonably dense, so a loose stone feels heavier than glass of the same size and shows no doubling of facet edges when viewed with a loupe. Many red glass imitations contain bubbles or swirl marks that garnet never shows.

Are garnets magnetic?

Slightly, and it is a genuine identification aid. The iron and manganese in most garnet species produce a weak magnetic response that a strong neodymium magnet can detect on a loose stone, which helps separate garnet from ruby and spinel. The response varies by species and is not a substitute for testing.

Are garnets heated or treated?

Almost never. Garnet is one of the few colored gemstones that reaches the market essentially untreated, so its color and clarity are natural. The main exception is some demantoid, which may get a low-temperature heat to soften brown tones, a stable and hard-to-detect change. For most garnet, what you see is what nature made.

Is garnet just an inexpensive red stone?

No. Garnet is a whole family of related minerals, not one gem. Common red almandine and pyrope are affordable, often a few dollars to around one hundred per carat. But green tsavorite and demantoid garnets are rare and can sell for thousands of dollars per carat, sometimes rivaling fine sapphire or ruby. The name covers a huge price range.

What is the most valuable type of garnet?

Demantoid, a brilliant green garnet with more fire than diamond, is the most valuable, especially Russian stones showing fine horsetail inclusions. Grass-green tsavorite from East Africa is next. Vivid orange mandarin spessartite and rare color-change garnets also command strong prices. Fine examples of these can run into the thousands of dollars per carat.

Why are tsavorite and demantoid so much more expensive than red garnet?

Rarity and color. Red almandine and pyrope are mined widely and in large sizes, so they stay affordable. Tsavorite and demantoid form under unusual conditions, are seldom found clean above a few carats, and show vivid green. Demantoid also has exceptional fire. Like nearly all garnet they are untreated, so fine clean stones are genuinely scarce.

Are garnets valuable?

It depends entirely on which garnet. Common red almandine and pyrope are inexpensive and widely available. Demantoid, tsavorite, fine spessartine and colour-change garnet are genuinely rare, and demantoid with horsetail inclusions from the Russian Urals reaches prices that rival fine emerald.

Is garnet hard enough for everyday jewelry?

Usually yes. Garnets range from about 6.5 to 7.5 on the Mohs scale and have no cleavage, so they resist chipping better than many softer stones. Varieties at 7 or above handle daily wear in rings well. Clean with warm soapy water and a soft brush, and do not leave the piece soaking overnight.

Can garnet go in an ultrasonic cleaner?

Usually yes for the common red varieties, which sit around 7 to 7.5 on the Mohs scale. Demantoid is softer at 6.5 and more often included, so treat it with more caution. Avoid ultrasonic on any garnet showing visible fractures, and never use steam on demantoid.

Which month is garnet the birthstone for?

January. Garnet is also the traditional gift for a second wedding anniversary. Because garnet is a mineral group rather than a single species, the month legitimately covers green tsavorite and demantoid and orange spessartine as well as the familiar deep red almandine.

What does garnet symbolise?

Garnet has long been associated with safe travel and returning home, and it was carried by travellers in the ancient and medieval world for that reason. The name comes from the Latin granatum, the pomegranate, whose seeds the deep red crystals resemble.