SILICATES; INOSILICATES; AMPHIBOLE GROUP · MONOCLINIC

Edenite

NaCa₂Mg₅Si₇O₂₂(OH)₂

Hardness: 5–6
Streak: White
Spec. Gravity: 3.0–3.1
System: Monoclinic

About

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.

Crystal Forms & Aggregates

Crystals are mostly tabular or in platy groups. Also in rounded individual crystals that are equant in size. Rarely fibrous or acicular.

Other ID Marks

Fluoro-edenite may be strongly fluorescent.

Striking Features

Cleavage angles and environment

Environment

In metamorphosed marble.

Varieties

✓ common · ✗ uncommon

Ferro-edenite— 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
Fluoro-edenite— 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

Noteworthy Localities

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.