ephesite

{{infobox mineral | name = Ephesite | image = Ephesite-120783.jpg | imagesize = 260px | alt = | caption = | category = Phyllosilicate minerals | group = Mica group, trioctahedral mica group | formula = NaLiAl2(Al2Si2)O10(OH)2 | IMAsymbol = Eph | strunz = 9.EC.20 | dana = | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/c also reported is a triclinic polytype | unit cell = a = 5.12, b = 8.853 c = 19.303 [Å]; beta = 95.08°; Z = 4 | color = Brownish pink, pearl gray, pale green | habit = Flakes | twinning = Commonly twinned about [310] or [30] | cleavage = Perfect on {001} | fracture = | tenacity = Brittle | mohs = 3.5–4 | luster = Vitreous, pearly on cleavage | streak = | diaphaneity = Translucent | gravity = 2.984 | density = | polish = | opticalprop = Biaxial (-) | refractive = nα = 1.592 - 1.595 nβ = 1.624 - 1.625 nγ = 1.625 - 1.627 | birefringence = δ = 0.033 | pleochroism = | 2V = 18° to 28° | dispersion = r > v strong | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }} Ephesite is a rare member of the mica silicate mineral group, phyllosilicate. It is restricted to quartz-free, alumina rich mineral assemblages and has been found in South African deposits in the Postmasburg district as well as Ephesus, Turkey.

== Composition == Ephesite has an ideal chemical formula of NaLiAl2(Al2Si2)O10(OH)2. Ephesite and paragonite are closely related due to their substitution of sodium in place of potassium. The general form of most micas, which can vary such as in the place of ephesite, can be written as W(X,Y)2-3Z4O10(OH,F)2 as observed by many sources. In the case of ephesite the W compound is sodium and the (X,Y) is lithium and aluminium, it also bears two hydroxides as the end members.