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Garnet comes from the Latin word granatus, which means grain.
That is because many garnet deposits are small grains of red crystals in or on their host rock.
Garnets have several “species”, or “families”, as well as several colors and varieties.
Chemistry: Mg3Al2Si3O12
Crystallography: Isometric
Refractive index: 1.73 – 1.76
Hardness: 7 – 7.5
Specific gravity: 3.65- 3.87
Dispersion: 0.022
Cleavage: None
Hear sensitive: Some
Pyrope comes from a Greek word meaning fire-like.
The typical dark red garnets are a mixture of pyrope and almandine (hereunder).
One popular garnet is chrome pyrope, whose color rivals ruby.
These are found in Arizona, where ants bring them to the surface.
While their color is superb, they are very dark in tone.
These gems are rarely faceted in sizes over one carat because of this.
One of the classic sources of this garnet is Alabanda, in Asia Minor.
The Roman historian Pliny wrote of them.
Chemistry: Fe3Al2Si3O12
Crystallography: Isometric
Refractive index: 1.75 – 1.83
Hardness: 7 – 7.5
Specific gravity: 3.95- 4.30
Dispersion: 0.024
Cleavage: None
Hear sensitive: Some
Our common, dark red garnets are a blend of almandine and pyrope.
Throughout history, it has been one of the most popular gems.
They are found worldwide and in great abundance, hence its low value.
Huge crystals exist, but because of their dark tone, only small to medium-sized gems are faceted.
These are cut very shallowly, to let light pass through.
Almandine garnets from Idaho and India sometimes have asbestos fiber inclusions.
These will produce star stones when properly cut.
They are highly prized by collectors because of their rarity.
They are also one of the most difficult gems to cut.
Chemistry: Mn3Al2Si3O12
Crystallography: Isometric
Refractive index: 1.79 – 1.83
Hardness: 7 – 7.5
Specific gravity: 3.80- 4.25
Dispersion: 0.027
Cleavage: None
Hear sensitive: Some
This garnet is named after Spessart, Bavaria.
Spessartite is somewhat rare.
As with the other garnets, it always occurs in a blend with other species.
Gems with the highest spessartite content are light orange.
Those with almandine content are reddish, to red-brown in hue.
The most valuable spessartites are a bright orangish-red.
These come from Ramona, California, and Amelia, Virginia.
Chemistry: Ca3Fe2Si3O12
Crystallography: Isometric
Refractive index: 1.86 – 1.95
Hardness: 6.5 – 7
Specific gravity: 3.70- 4.10
Dispersion: 0.057
Cleavage: None
Hear sensitive: Some
The name comes from Dutch, meaning “diamond-like” in reference to its incomparable brilliance and fire.
Demantoid, by definition, is always green, but the exact shade ranges from a very strong yellowish-green to nearly the color of fine emerald.
Many stones have a brownish cast.
Stones with more intense green coloration are more highly valued, but lighter stones display substantially more fire.
This is one of the rarest and most sought after garnets.
Its dispersion is much higher than any other garnet and even higher than diamond.
Dark body colors usually mask the dispersion, but small, light-colored gems are dazzling!
Demantoids are known for their distinctive, horsetail inclusions.
They are both an aid to the gemologist and a delight to collectors.
Chemistry: Ca3Al2Si3O12
Crystallography: Isometric
Refractive index: 1.72 – 1.80
Hardness: 6.5 – 7.5
Specific gravity: 3.40- 3.70
Dispersion: 0.028
Cleavage: None
Hear sensitive: Some
The botanical name for gooseberry is grossularia, from which this garnet receives its name.
Unlike the other garnets, grossulars are rarely red or dark.
They come in every color except blue and are sometimes colorless.
The tone is often light to medium.
They make brilliant gems with vibrant colors.
Some say the name rhodolite comes from the Greek word, rhodon, meaning rose.
Other scholars compare the name to rhododendron.
In either case, the name is comparing the color to a flower.
Malaia garnet or Malaya garnet is a gemological varietal name for light to dark pinkish-orange, reddish-orange, or yellowish-orange garnet, which is a mixture of pyrope and spessartite.
It is found in east Africa, in the Umba Valley bordering Tanzania and Kenya.
Malaia was at first believed to be a type of spessartite garnet.
During the 1970’s rough malaia garnets were mixed with parcels of Rhodolite garnet being offered for sale.
These odd color stones were rejected, and the name given to this type of garnet was malaia, which is a Swahili word meaning “outcast.”
It came into usage for a number of garnets that did not fit into any of the standard categories.
Tsavorite is named after its only source, the Tsavo Valley, in Kenya.
It is the chromium colored, green variety of grossularite.
These popular gems demand high value in today’s market.
While faceted stones approaching 20 carats are known, their deep coloring usually keeps their size below three carats.
Hessonite is from a Greek word meaning inferior.
This refers to it having less hardness than other garnets.
Hessonites are an orangish variety of grossular garnet.
Sometimes their coloring leans towards the pink.
Asbestos, Québec, is one of the most common sources.
The miners find pinkish-orange crystals among the asbestos.
Africa is also a major source of hessonite.
Any gem that changes color is a rare find and a treat for collectors.
Garnets exhibit the widest variety of color changes in the gem world, with almost every hue shown.
It is commonly said that garnets come in every color of the rainbow except blue.
This is still true in natural light, but there has been discoveries of garnets that turn blue in artificial light.
Color change garnets are mostly pyrope and spessartite in composition.
Except for the color change, they are identical in properties to the Malaia variety.
Their primary source is Africa.
Idaho garnets, which are primarily almandine/pyrope mixtures, occasionally show a strong color shift from red to purplish-red.
