Garnet: A Rainbow Of Gemstone Colors

The birthstone for January has been the traditional red Garnet, a wonderful warm color for those of us living in cold northern temperatures. But nature continues to surprise us with the colors available for this gemstone. Green Garnets have been known and identified as Garnet for at least 150 years. Garnets have been identified in shades of orange, yellow, purple, and pink for a long time, and in recent years, the existence of blue Garnets has been established.

How can one gemstone have so many colors? Garnets are actually a large family of related silicate minerals. The only ingredients common to all varieties of garnet are oxygen and silicon, two common elements. The other elements present, the ones that cause the wide variety of colors , normally come from two ‘groups’. The first group includes calcium, magnesium, ferrous iron, and manganese; the second group includes aluminum, ferric iron, chromium, and titanium. Take one or more elements from the first group, and one or more elements from the second group, and combine them with the silicon and oxygen, and you have a garnet. Elements can substitute for each other, and some Garnets appear to be hybrids of other Garnets, creating a stunning and wide array of colors. While some folks equate Garnet with the dark red color of the traditional stones, the mineral continues to surprise the gemologists of the world, with new varieties surfacing from time to time.

The two best known Garnets, and ones that have been used for thousands of years in jewelry and decorative items, are Almandine Garnet and Pyrope Garnet.

This variety, also known as Almandite, takes its name from Alabanda, a city in what is now Turkey. This was a gem cutting center in ancient times, and Pliny the Elder called the stones "alabandicus". These Garnets have a deep red color, often slightly purple, created by their iron and aluminum components. They were often cut en cabochon, with a domed top, and these were referred to as "carbuncles". Almandine garnets are probably the most abundant variety of Garnet, and India, Sri Lanka, Madagascar, and Brazil are the major modern sources of the stone. They are also found in the United States. The stones have been marketed as Oriental Garnets, and also as Almandine Ruby, which is an inappropriate misnomer.

This magnesium-aluminum Garnet has a deep red color. This is the traditional ‘Bohemian Garnet’ used in European jewelry for centuries. Large, fine quality specimens are rare, but stones are readily available in finished sizes of 5mm and smaller. The name Pyrope means “similar to fire”or “fire-eyed”, and some stones do exhibit a wonderful “glow”. Some very fine specimens, known as Chrome Pyropes, exhibit an intense red color reminiscent of finer Red Spinel or Ruby. Pyrope Garnets are produced in the Czech Republic, South Africa, Australia, and the United States, along with other less important sources. The stones are sometimes marketed, incorrectly, with misleading names such as Cape Ruby, Colorado Ruby, and Arizona Ruby.

The name Garnet comes from the the Latin granatus, meaning “seed” or “grain”. This may be due to the existence of garnet in small crystals that resemble grains, or even pomegranate seeds. These small crystals, of little or no gemological use, have been used as an abrasive, with Pyrope and Almandine varieties being most often used for this purpose.

Now for the rarer varieties of Garnet:

This violet-red and lilac-red variety of Garnet is actually a blend of Almandine and Pyrope,both of which seldom occur in a pure chemical composition. Rhodolite Garnet is most often about 2 parts Pyrope and 1 part Almandine. The main sources for this variety are Sri Lanka, Tanzania, Zimbabwe, and Madagascar. It is also found in the United States. It is incorrectly represented with misnomers such as Cape Ruby, Arizona Ruby, California Ruby, and Rocky Mountain Ruby.

This popular gem variety of Garnet is a relative newcomer to the jewelry world. Discovered in 1967, near Lake Tsavo in Kenya, it was nitially marketed by Tiffany & Company. The deep green color is similar to the finest Chrome Green Tourmalines. Jewelry featuring Tsavorite Garnet will normally date from the 1970s or later, but there is always a chance that an older piece of jewelry will feature the stone, from a time before its proper identity was known. It is a variety of Grossular Garnet.

This reddish-yellow Garnet is also a variety of Grossular Garnet. In the past, it was sometimes referred to as Jacinth, Hyancinth, or Cinnamonstone. Some older stones, originally identified as Zircon, have proved to be this variety of Garnet. In antiquity, the names Jacinth and Hyacinth were also used for these Zircons of similar color, so the actual identity of any stone identified by these names in older writings is always in question.

Grossular Garnets are found mainly in Sri Lanka, Kenya, and Tanzania, but also in India, Brazil,Canada, and the United States.

This Garnet is one of the rarer varieites that is sought after. Peter Carl Fabrege favored this brilliant green Garnet, originally found in the Ural Mountains, and many older pieces that feature the stone are products of fine Russian goldsmiths and jewelers of the 19^th century. The Russian material often can be identified by a "horse tail" inclusion not known to be present in specimens from other parts of the world. Relatively large finds were discovered in Namibia in the 1990s, and it may also be found in some mmountainous regions of the Middle East and in Italy. It is a variety of Andradite Garnet.

Two other gem varieties of Andradite Garnet exist, with little use in jewelry. Topazolite has a yellow-green color and sometimes displays a chatoyant cat’s-eye effect. Melanite is a black variety.

Named after Spessart, the German location where it was first mined, it is also referred to as Spessartine. This variety of Garnet is found in a number of African, Middle Eastern, and South American locations. A orange-yellow variety from Madagascar is sometimes marketed as Mandarin Garnet, and a reddish-orange variety has been found in several locales in the United States.

This gem was first identified as a Garnet in the 1960s, when large finds were made in the Umba Valley of Tanzania and Kenya. It is a blend of Pyrope and Spessartite Garnet, with a bit of Almandine and Grossular Garnet sometimes thrown into the mix. It often displays nicer color under incandescent light than under natural light, which causes some to consider it a ‘night stone’.

This variety of Garnet was first noticed in the early 20^th century, in South Africa. It resembles Jadeite, and is probably actually rarer than Jadeite. Incorrectly marketed with names such as Transvaal Jade and South African Jade, it has never seen much use in jewelry. Lower quality Hydrogrossular Garnet has also been discovered in Canada. This material is sometimes incorrectly marketed as African Jade, despite the fact that it is neither African or Jade.

This is one of the rarest of Garnets, with a beautiful emerald green color. However, most specimens are small, or opaque, or both. The drusy form of the material is occasionally used in jewelry, and few clean faceted stones exist.

There was a debate for some time over whether Blue Garnets actually existed. This has been confirmed, with specimens that appear to be a mix of Pyrope and Spessartite Garnet, with a few other varieties sometimes added to the mix. The element Vanadium seems to be the cause of the blue color. Specimens from Madagascar were first identified in the 1990s.

As if this fantastic range of color were not enough, some Garnets also exhibit some special optical properties.

Chatoyancy, the "cat’s-eye" effect is exhibited by some Topazolite Garnets.

Asterism, the "star effect" most associated with Star Sapphire, is also seen in some Garnets. Almandine Garnets are the only variety known to exhibit this effect. This appears to be the result of needles of Rutile in the stone, with 4-pointed stars being more common than 6-pointed stars. Garnets from Idaho are the only ones known to show the 6-pointed star, although the 4-pointed ones are commoner. Star Garnet is the state gemstone for Idaho. Brazil, India, and Russia also produce some Star Garnets.

Color change is a rare phenomenon in gemstones. Some Malaya Garnet was known to exhibit this property, with a color change from a grayish-green or purplish green to a reddish-pink or reddish-purple or lavender, when moved from natural light to incandescent light. Some of the newer Blue Garnets produce a similar change.

There are two man-made Garnets which have seen use in jewelry. Neither actually has a natural counterpart, so man-made is probably a more appropriate term than synthetic. Yttrium aluminum garnet and gadolinium gallium garnet have both been used as Diamond simulants, although now displaced by more convincing simulant materials. These materials also have industrial applications.

Garnet is sometimes simulated by synthetic Corundum in a red garnet color, and this material is sometimes used in inexpensive birthstone jewelry and Mother’s rings.

Low quality garnet has found use as an industrial abrasive. It was first used for sandpaper production in the 1870s. Over 100,000 tons of Garnet per year are used as industrial abrasives. Garnet is also used in specialized fields of geology to obtain clues about the heat and pressure history of surrounding materials. In some parts of the world, the presence of certain varieties of Garnet indicates the presence of Kimberlite, which indicates the possibility of Diamonds in the area.

The hardness of Garnet varies a bit, due to the differences in actual composition. Hardness ranges from 6.5 to 7.5 on the Moh’s Scale. Garnet should not be steam cleaned. Ultrasonic cleaning is usually safe. However, the presence and type of inclusion in the stone may have an effect on durability, and we do not recommend the practice.

Garnet is one of few gemstones which is not being enhanced to improve its color. Some Garnets are treated with an Azotic coating of questionable durability, and marketed as Mystic Garnet. Special care is needed with any of these coated stones.