tschermakite

{{infobox mineral | name = Tschermakite | category = Silicate mineral (amphibole) | image = Anyolite, pargasite, rubis 3.jpg | imagesize = 260px | alt = | caption = Anyolite, a metamorphic rock: chrome-zoisite (bright green), tschermakite (black), ruby (red) | formula = Ca2(Mg3Al2)(Si6Al2)O22(OH)2 | IMAsymbol = Tsr | molweight = | strunz = 9.DE.10 | dana = | system = Monoclinic | class = Prismatic (2/m) (same H-M symbol) | symmetry = C2/m | unit cell = a = 9.762(6) Å b = 17.994(12) Å c = 5.325(6) Å; β = 105.10(8)°; Z = 2 | color = Medium to dark green to green-black to black, brown (rare) | colour = | habit = As prismatic crystals or as reaction rims on other minerals | twinning = Simple or multiple twinning parallel to {100} | cleavage = Perfect on {110} Parting on {100}{001} | fracture = Conchoidal | tenacity = Brittle | mohs = 5–6 | luster = Vitreous | streak = Pale grey-green | diaphaneity = Transparent | gravity = 3.15 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.623–1.660 nβ = 1.630–1.680 nγ = 1.638–1.688 | birefringence = δ = 0.015–0.028 | pleochroism = Visible in browns and greens | 2V = Measured: 60° to 90° | dispersion = | extinction = | length fast/slow = | fluorescence= | absorption = | melt = | fusibility = | diagnostic = | solubility = | other = | alteration = | references = }}

The endmember hornblende tschermakite () is a calcium-rich monoclinic amphibole mineral. It is frequently synthesized along with its ternary solid solution series members tremolite and cummingtonite so that the thermodynamic properties of its assemblage can be applied to solving other solid solution series from a variety of amphibole minerals.