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The edenite Mineral Group
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Edenite is a member of the extended Hornblende group. There are
several variations of Edenite with different elemental
substitutions. Some of these are recognized as individual minerals,
thereby making Edenite a mineral group, with Edenite the
dominating member. Edenite is named after the hamlet of Edenville, New York, the type locality where this mineral was first described. |
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Chemical Formula |
NaCa2Mg5Si7O22(OH)2
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Composition |
Basic sodium, calcium, and magnesium silicate |
| Variable Formula |
NaCa2(Mg,Fe2+)5Si7O22(OH,F)2
The above formula encompasses all the recognized member minerals of the extended Edenite group
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Color |
Light green, dark green, greenish-gray, gray, black. Rarely white, tan, or yellow. |
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Streak |
White |
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Hardness |
5 - 6 |
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Crystal System |
Monoclinic |
Crystal Forms
and Aggregates |
Crystals are mostly tabular or in platy groups. Also in rounded individual crystals that are equant in size. Rarely fibrous or acicular.
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Transparency |
Translucent to opaque |
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Specific Gravity |
3.0 - 3.1 |
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Luster |
Vitreous |
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Cleavage |
1,2 - prismatic |
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Fracture |
Uneven |
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Tenacity |
Brittle |
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Other ID Marks |
Fluoro-edenite may be strongly fluorescent.
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In Group |
Silicates; Inosilicates; Amphibole Group |
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Striking Features |
Cleavage angles and environment |
| Environment |
In metamorphosed marble.
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| Rock Type |
Metamorphic |
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Popularity (1-4)
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3 |
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Prevalence (1-3)
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2 |
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Demand (1-3) |
2 |
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Edenite is the name of an individual mineral, as well as group name
for a few similar Edenite-related minerals with slight variations
of
elements in their chemical formula. Edenite is the
magenesium and hydroxyl-rich form of this series, and the other forms the recognized by the IMA as individual minerals are listed below.
- Variety of Edenite where iron replaces the magnesium content. Ferro-edenite is recognized by the IMA as a distinct mineral species with the following chemical formula: NaCa2Fe2+5Si7O22(OH)2
- Variety of Edenite where fluorine replaces some the hydroxyl content.
Fluoro-edenite is recognized by the IMA as a distinct mineral species
with the following chemical formula: NaCa2Mg5Si7O22(F,OH)2
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Edenite is probably more common than perceived, and can sometimes be perceived as Hornblende and not further identified. Dark crystal groups of Edenite were found in the Franklin marble at Amity and Edenville, Orange Co., New York, and across the border in Franklin and Ogdensburg, Sussex Co., New Jersey. In Canada, large crystals have come from several localities in Wilberforce, Monmouth Township, Haliburton Co., Ontario. Small crystals were also found in Mont Saint Hilaire, Quebec.
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Have a question about Edenite? Visit our Q&A Community and ask the experts!
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