kyanite

{{Infobox mineral | boxbgcolor = #6a829f | boxtextcolor = #FFFFFF | name = Kyanite | category = Nesosilicate | image = Kyanite_crystals.jpg | imagesize = 260px | caption = | formula = | IMAsymbol = Ky | strunz = 9.AF.15 | system = Triclinic | class = Pinacoidal () (same H-M symbol) | symmetry = P | unit cell = a = 7.1262(12) Å b = 7.852(10) Å c = 5.5724(10) Å α = 89.99(2)°, β = 101.11(2)° γ = 106.03(1)°; Z = 4 | color = Blue, white, rarely green, light gray to gray, rarely yellow, pink, orange, and black, can be zoned | habit = Columnar; fibrous; bladed | twinning = Lamellar on {100} | cleavage = [100] perfect [010] imperfect with 79° angle between | fracture = Splintery | tenacity = Brittle | mohs = 4.5–5 parallel to one axis 6.5–7 perpendicular to that axis | luster = Vitreous to white | refractive = nα = 1.712 – 1.718 nβ = 1.720 – 1.725 nγ = 1.727 – 1.734 | birefringence = δ = 0.012 – 0.016 | opticalprop = Biaxial (-); high relief | pleochroism = Trichroic, colorless to pale blue to blue | 2V = 78°–83° | streak = White | gravity = 3.53–3.65 measured; 3.67 calculated | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to translucent | other = | references = }}

Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks generally indicates metamorphism deep in the Earth's crust. Kyanite is also known as disthene or cyanite.