fluorapophyllite-(K)

{{Infobox mineral | name = Fluorapophyllite-(K) | category = Phyllosilicate minerals | group = Apophyllite group | boxwidth = | boxbgcolor = | image = Apophyllite-(KF)-Gyrolite-145017.jpg | imagesize = 260px | caption = | formula = KCa4Si8O20(F,OH)·8(H2O) | IMAsymbol = Fapo-K | molweight = | strunz = 9.EA.15 | system = Tetragonal | class = Ditetragonal dipyramidal (4/mmm) H–M symbol: (4/m 2/m 2/m) | symmetry = P4/mnc | unit cell = a = 8.963(2), c = 15.804(2) [Å]; Z = 2 | color = Colorless, white, pink, pale, yellow, green; in thin section, colorless | habit = Tabular to prismatic crystals; may be pseudocubic | twinning = Rare on {111} | cleavage = Perfect on {001}, imperfect on {110} | fracture = Uneven | tenacity = Brittle | mohs = 4.5–5 | luster = Vitreous, pearly on {001} | refractive = nω = 1.530 – 1.536 nε = 1.532 – 1.538 | opticalprop = Uniaxial (+) | birefringence = δ = 0.002 | dispersion = High, may be anomalous | pleochroism = | streak = | gravity = 2.33–2.37 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | references = }}

Fluorapophyllite-(K), formerly known as apophyllite-(KF) and sometimes simply referred to as fluorapophyllite, is the most common mineral of the apophyllite group, with the chemical formula of KCa4Si8O20(F,OH)·8(H2O). It gets the first part of its name, "fluor", because it contains more fluorine than hydroxide compared to the other minerals in the apophyllite group.