Geology Home Page physical geology historical geology planetary gems
Roger Weller, geology instructor
by Jessee Tellez
Garnet Types Around the World
What is garnet?
Garnet, the birthstone for those born in January, is a hard silicate mineral group commonly found in metamorphic rock. Garnet has a hardness ranging from 6.5 to 7.5 on the Mohs scale. It has historically been used for jewelry, decoration, and currency by the Ancient Romans and worn by Egyptian pharaohs. Most people associate garnet with the color red but it comes in many different shades and hues. Garnet comes in more than twenty varieties and the five of them that are most commonly used as gems are: pyrope, almandite, spessartite, grossularite, and andradite. There are also garnets that are combinations of those five varieties and which adds to the number of possible colors and shades. These garnet types are found all across the world, even here in our home state of Arizona.
Pyrope, the most common type of red garnet, is said to resemble rubies and even pomegranate seeds. In fact, its name comes from the Greek word “puropus”, which is made of the words “pur” for “fire” and “ops” for “eye”. So, “pyrope” fittingly means “fiery-eyed”. Even though pyrope is known for its red tint, it can range from purple to blood orange to almost black. It can be found in Madagascar, Myanmar (Burma), South Africa, China, Sri Lanka, and Tanzania. Pyrope is also found in the United States in states such as Arizona, New Mexico, Utah, North Carolina, and Montana. The Czech Republic is also historically known for being a major source of pyrope. Garnets found there are called Bohemian garnets and are believed to “ward off melancholy and inspire optimism.”
Another type of garnet that is most commonly red
is almandite. Almandite can also be purplish-red, brownish-red, and orangey-red
if mixed with other garnet types, like pyrope or spessartite. Only a fraction of
naturally occurring almandites are used as gems due to their lack of clarity and
their opaqueness. They are instead poplar in the industrial sector for purposes
like sandblasting. Like pyrope, almandite is found in the Czech Republic,
Madagascar, Sri Lanka, and the United States. Idaho, Pennsylvania, and Nevada
are states with almandite deposits, just to name a few.
garnets can range from orange to reddish-brown and in some cases, appear to be a
warm yellow color. Spessartite garnets with a vibrant yellow-orange color,
especially those found in deposits in Namibia, are sometimes referred to as
Mandarin garnets. The orangey colors are due to the manganese in the minerals.
Spessartite garnets got their name from the Spessart mountain range in Germany
where it was found and mined in the 1880s. However, this type of garnet was not
used as a gemstone for jewelry until over 100 years later when it was mined in
Namibia and Mozambique. Spessartite can also be found in Sri Lanka, Brazil,
Madagascar, China, Kenya, and the U.S. (e.g. California, Nevada, and Colorado).
Grossularite is a very diverse
category of garnet. It can be colorless, yellow, green, brown, ember-colored,
white, black, or gray. Grossularite gets its name from the botanical word for
gooseberry: grossularia. There are deposits of grossularite in Canada, Mexico,
Russia, Tanzania, Pakistan, Sri Lanka, and in the United States in Vermont,
Utah, California, and New York. However, Kenya is the most popular grossularite
producer. Tsavorite, a rare deep green grossularite garnet, is found only on the
border of Kenya and Tanzania and is extremely valuable.
Andradite is not as common as pyrope or almandite but it still used in jewelry. The ones used as gems are more commonly called demantoid or topazolite. Andradite is named after the Brazilian mineralogist who discovered it: José Bonifácio de Andrada e Silva. It comes in various colors, ranging from dark yellow to black to green to brown. You can find deposits of it in Russia, Mali, Italy, Namibia, Madagascar, Iran, and America (in California, Arizona, and Connecticut). Arizona is actually home to a famous andradite location: Stanley Butte in the San Carlos Indian Reservation in Graham County.
Where Else Is There Garnet?
As you can tell by now, garnet is found in a multitude of places on almost every continent. Even so, there are still undiscovered areas where garnets await to be found. Along the Himalayas and in parts of Afghanistan, there are suspected sources of garnet and we will have to see where else in the world we will find deposits.