ReferencesNov. 19, 2003Mineralogy 231Lecture 31: zipper silicate, health hazards: amphibolesFriday: alteration minerals: kaolin, pyrophyllite, talc, serpentinereadings: N 239-244; K 463-465, 472, 528-534; DHZ, 324-331, 357-362classification of Ca and Na amphiboles DHZ (1997), Fig. 7vertical axis is Na in B site replacing Ca via NaAl for CaMg, horizontal axis AlVIAlIV for MgVISiIVvery complex, and moreover there is yet another name for the Fe equivalents of each speciesalthough diagram implies continuous solid solutions, there are solvus gaps at low Tcalcic amphibolesspecific name varies with Mg-Fe solid solution for different Al and Na contentsvary from colorless in thin section to green, olive, brown; white to green to black in hand specimen2V from high +, more commonly high -; RI medium to high, Z  c low (10-30°, compare >30° for cpx)actinolite group, Ca2(Mg,Fe)5Si8O22(OH)2most common in marbles, greenschists, calc-pelites, metamorphosed ultramafic rocksactinolite is group name for tremolite-ferroactinolite solid solution Fig. on p. 283tremolite, Ca2Mg5Si8O22(OH)2ferroactinolite, Ca2Fe5Si8O22(OH)2phase equilibria for actinolite, ferroactinolite K, Fig. 12.48reaction for tremolite decomposition DHZ (1997), Figs. 66, 67hornblende group, hydroxyl Na-Ca-Mg-Fe-Al silicatecommon in marbles, metabasalts (amphibolites), basalts Fig. on p. 285sodic hornblendes: pargasite, hastingsite, edenite are common in marbles, amphibolitessome evidence for a solvus gap between actinolite and hornblende at 450-500°Cquadrilateral amphiboles (Ca-Mg-Fe amphiboles)analogous plot to that for pyroxenesCa2Mg5Si8O22(OH)2 - Ca2Fe5Si8O22(OH)2 - Mg7Si8O22(OH)2 - Fe7Si8O22(OH)2 Fig. 14.13calcic actinolite group separated by wide solvus from ferromagnesian anthophyllite and gruneritegrunerite solid solution extends all the way to Fe end-member (correct Nesse's diagram)phase diagram for quadrilateral amphiboles K, Fig. 11.21sodic amphibolestypically pleochroic in blue, violet colors, variable 2Vglaucophane, Na2Mg3Al2Si8O22(OH)2Fig. on p. 283riebeckite, Na2Fe3Fe2Si8O22(OH)2glaucophane common in blueschistsriebeckite common in iron formations, some alkaline granitescomposition plot involving Mg vs. Fe2+, Al vs. Fe3+ has four Na amphiboles Fig. 14.19glaucophane, ferroglaucophane, magnesioriebeckite and riebeckiteglaucophane breaks down below 6-8 kbar at 300-400°C with several complex reactions, including:glaucophane + lawsonite = albite + clinochlore + clinozoisite + quartz + water:5Na2Mg3Al2Si8O22(OH)2 + 12CaAl2Si2O7(OH)2.H2O = 10NaAlSi3O8 + 3Mg5Al2Si3O10(OH)8 + 6Ca2Al3Si3O12(OH) + 7SiO2 + 14H2Oleft-hand side is blueschist facies assemblage, right-hand side is greenschist facies assemblagemust correct locus for Mg-Fe2+, Al-Fe3+ solid solutions in glaucophane, epidote, chloriteglaucophane-actinolite solvus, also intermediate ss, winchite, T of crest ca. 400°C (EJE est.)glaucophane-hornblende solvus, also intermediate ss, barroisite, T of crest ca. 500°C (EJE est.)health hazards of amphibolesfibrous amphiboles were a common choice for asbestos what was the use of asbestos?fibrous grunerite ("amosite") K, Fig. 12.47fibrous riebeckite ("crocidolite") K, Fig. 12.50pyriboles, biopyribolesTEM observations with horizontal c axis, (010) plane, chains or "zippers" K, Fig. 11.27, p. 462double chains: anthophyllitetriple chains: jimthompsonitedouble and triple chains: chesteritemixtures of sheets and chains also known in biopyribolesReferencesDeer, W.A., Howie, R.A. & Zussman, J. (1997) Volume 2B, Rock-Forming Minerals: Double-ChainSilicates, 2nd. ed., The Geological Society, London, 764 p.Deer, W.A., Howie, R.A. & Zussman, J. (1991) An Introduction to The Rock-Forming Minerals, 2nd ed.,Longman, NY, 696 p.Veblen, D.R. (1981) Amphiboles and other hydrous pyriboles – mineralogy. Rev. Mineral. 9A, 372 p.Veblen, D.R & Ribbe, P.H. (1982) Amphiboles and other hydrous pyriboles: petrology and experimentalphase relations. Rev. Mineral. 9B, 390