edenite

{{Infobox mineral | name = Edenite | category = Amphibole mineral | boxwidth = | boxbgcolor = | image = Edenite-188165.jpg | imagesize = | caption = Edenite crystal from Bancroft District, Ontario | formula = NaCa2Mg5(Si7Al)O22(OH)2 | IMAsymbol = Ed | molweight = 834.25 g/mol | strunz = 9.DE.15 | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m | unit cell = a = 9.83, b = 17.95 c = 5.3 [Å], β = 105.18°; Z = 2 | color = White to gray, pale to dark green, also brown and pale pinkish-brown | habit = Prismatic crystals, fibrous, as reaction rims on pyroxenes | twinning = Simple or multiple parallel to {010} | cleavage = Good on (110) | fracture = Conchoidal | tenacity = Brittle | mohs = 5–6 | luster = Vitreous | refractive = nα = 1.606 – 1.649, nβ = 1.617 – 1.660, nγ = 1.631 – 1.672 | opticalprop = Biaxial (+) | 2V = 50–82° | birefringence = δ = 0.025 | pleochroism = Distinct, greens, blue-greens, and yellow-browns | streak = White | gravity = 3.05–3.37 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Semitransparent | other = | references = }} Edenite or edenitic hornblende is a double chain silicate mineral of the amphibole group with the general chemical composition NaCa2Mg5(Si7Al)O22(OH)2. Edenite is named for the locality of Edenville, Orange County, New York, where it was first described.

== Occurrence == Edenite has been found primarily in metamorphic rocks, occurring in pods of other magnesium-rich minerals within a marble formation or with garnet-rich lherzolites from deep within the Earth's crust. Thus, finding edenite in the field can indicate high-temperature regional metamorphism of the surrounding rocks.