andesine

{{Infobox mineral | name = Andesine | category = Tectosilicate minerals | group = Feldspar group | series = Plagioclase feldspar series | boxwidth = | boxbgcolor = | image = Andesine-251551.jpg | imagesize = 260px | caption = Andesine | formula = (Ca,Na)(Al,Si)4O8 (Na:Ca = 50:50 to 70:30) | IMAstatus = Variety of albite | molweight = | system = Triclinic | class = Pinacoidal () | symmetry = P (no. 2) | unit cell = a = 8.155 Å, b = 12.9 Å, c = 9.16 Å; α = 93.917°, β = 116.3333°, γ = 89.166°; Z = 8 | color = White, gray, green, yellow, flesh-red | habit = Crystals rare, to 2 cm; commonly massive or granular | twinning = Common following albite, pericline, and carlsbad twin laws | cleavage = Perfect on {001}, good on {010} | fracture = Uneven to conchoidal | tenacity = Brittle | mohs = 6 – 6.5 | luster = Subvitreous to pearly | polish = | refractive = nα = 1.543 – 1.554 nβ = 1.547 – 1.559 nγ = 1.552 – 1.562 | opticalprop = Biaxial (+/−) | birefringence = δ = 0.009 | dispersion = | pleochroism = | 2V = Measured: 76° to 83° | fluorescence= | absorption = | streak = White | gravity = 2.66 – 2.68 | density = | melt = | fusibility = | diagnostic = Requires optical/chemical analysis | solubility = | diaphaneity = Transparent to translucent | other = | references = }}

Andesine is a silicate mineral, a member of the plagioclase feldspar solid solution series. Its chemical formula is (Ca, Na)(Al, Si)4O8, where the ratio of albite to anorthite (Na:Ca) is 50:50 to 70:30. The formula may be written as Na0.5-0.7Ca0.3-0.5Al1.3-1.5Si2.5-2.7O8.