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Almandine in Schist Matrix

The Mineral almandine




Almandine is the most common member of the Garnet group. It is also a popular gemstone and the most widely used Garnet in the gem trade. More gemstones are faceted from Almandine than any other type of Garnet. Only a small amount of Almandine crystals are transparent and light enough for gemstone use; most of the Almandine found is rough and opaque and not gem quality. Some Almandine Garnets display asterism when polished as cabochons, and are known as "Star Garnets".

Almandine is often embedded in a mica schists, and forms very nice matrix pieces with perfectly formed symmetrical crystals. The schist matrix often breaks up due to weathering, resulting in the Almandine crystals breaking loose into individual, perfectly formed floater crystals which may be quite large.
Chemical Formula Fe3Al2Si3O12
Composition Iron aluminum silicate. The iron is sometimes partially replaced with magnesium and manganese.
Variable Formula (Fe,Mg,Mn)3Al2Si3O12
Color Dark red, reddish-brown, black. May also be multicolored black with reddish edges or tinges. Rarely pink or purple.
Streak Colorless
Hardness 7.5 - 8.5
Crystal System Isometric
3D Crystal Atlas
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Crystal Forms
and Aggregates
As well-formed dodecahedral and trapezohedral crystals, and occasionally in modified combinations of the two. Crystals may be striated or with stepped growth layers, and are sometimes warped into rounded ball-like forms. Also in dodecahedral crystal aggregates, grainy, massive, and as rounded waterworn crystals.
Transparency Transparent to opaque
Specific Gravity 4.3
Luster Vitreous
Cleavage None. May exhibit parting.
Fracture Conchoidal to uneven
Tenacity Brittle
Other ID Marks Paramagnetic (becomes magnetic upon heating).
In Group Silicates; Nesosilicates; Garnet Group
Striking Features Crystal form, color, and hardness
Environment In regional metamorphic environments in mica schist, and in contact metamorphic hornfels. Also in igneous rocks in diorite and granite pegmatites, and as a sedimentary mineral in alluvial deposits.
Rock Type Igneous, Sedimentary, Metamorphic
Popularity (1-4) 2
Prevalence (1-3) 1
Demand (1-3) 1

Almandine ON EBAY
OTHER NAMES
Alamandine
Almandite
Oriental Garnet

VARIETIES
 -  Refers to dark, brownish-red to black, opaque Almandine Garnet.
 -  Refers to a deep red, transparent form of Almandine or Pyrope Garnet.
 -  Almandine Garnet with a slightly purplish tinge.

USES
When transparent, Almandine Garnet makes a very popular gemstone. Almandine Garnets are used in all forms of jewelry, and along with Pyrope make the most popular dark red jewelry gemstone.
For more information, see the gemstone sections on Almandine and on Garnet.

Well formed Almandine crystals are very popular among mineral collectors. Almandine is also industrially important for use as an abrasive, and when used as a sandpaper, it is known as garnet paper.

NOTEWORTHY LOCALITIES
Almandine is a very common mineral, and is found worldwide. Only those localities which have produced excellent specimens are mentioned. Some of the best crystallized Almandine embedded in mica schist come from the classic locality of the Ziller valley, in the North Tyrol, Austria. Also high up in the Alps, in an occurrence spanning two countries, is the Granatenkogel Mountain, with the northern slope in the Ötztal, North Tyrol, Austria, and the southern slope in the Passiria Valley, Bolzano Province, Italy.

Other important worldwide occurences include Šumperk, Moravia, Czech Republic; the Altay Mine in the Koktokay pegmatite field, Xinjiang Autonomous Region, China; the Thackaringa District, Yancowinna Co., New South Wales, Australia; and Serrote Redondo, Pedra Lavrada, Paraíba, Brazil.

In the U.S., perhaps the most well-known occurrences are Garnet Ledge and the Sitkine River on Wrangell Island, Alaska. This locality produces excellent crystals embedded in a shiny mica schist matrix. The Barton Garnet Mine, in Gore Mountain, North River, Warren Co., New York, touts itself as the world's largest Garnet mine, producing extensive amounts of Almandine for use as garnet paper. Very large crystals have come from there, they are all crude and incomplete. Large and historic Almandine crystals were found in various construction projects on the island of Manhattan (New York Co.) in New York City, New York over the past two centuries. In fact, one the largest complete Almandine crystals ever found in the U.S. originated from Midtown Manhattan, and is dubbed the "Subway Garnet".

The New England states have a number of important Almandine occurrences, including Green's Farm, Roxbury, Litchfield Co., Connecticut (sadly this locality has just become closed to collectors); the Nathan Hall Quarry, East Hampton, Middlesex Co., Connecticut; the Russell Garnet mine, Russell, Hampden Co., Massachusetts; Greenwood, Oxford Co., Maine; and Mt. Apatite, Auburn, Androscoggin Co., Maine. Excellent trapezohedral crystals came from the Hedgehog Hill Quarry, Peru, Oxford Co., Maine.

Enormous Almandine crystals were found in the Sedalia Mine, Salida, Chaffee Co., Colorado, often coated with a mica layer; and lustrous dark crystals come from Garnet Hill, Ely, White Pine Co., Nevada. North Carolina has several localities, most noteworthy is Spruce Pine, Mitchell Co. Large Almandine crystals, including those that display asterism, are found at Emerald Creek, Latah Co; and Fernwood, Benewah Co., Idaho.

COMMON MINERAL ASSOCIATIONS
Biotite, Muscovite, Quartz, Staurolite, Andalusite, Hornblende, Epidote, Magnetite, Nepheline, Leucite, Corundum

DISTINGUISHING SIMILAR MINERALS
Pyrope - Can be indistinguishable by ordinary means, though Pyrope is much rarer and limited in its localities.
Grossular - Usually lighter in color than Almandine, and often found in specific localities where Almandine is not found; otherwise indistinguishable by ordinary means.
Andradite - Other than locality differences, Andradite and Almandite cannot be indistinguishable by ordinary means.
Spinel - Forms different crystals than Almandine.
Ruby - Harder (9), usually more intense red, different crystal forms.


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