{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,26]],"date-time":"2026-06-26T17:06:12Z","timestamp":1782493572707,"version":"3.54.5"},"reference-count":17,"publisher":"Mineralogical Society","issue":"361","license":[{"start":{"date-parts":[[2018,7,5]],"date-time":"2018-07-05T00:00:00Z","timestamp":1530748800000},"content-version":"unspecified","delay-in-days":11265,"URL":"https:\/\/www.cambridge.org\/core\/terms"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Mineral. mag."],"published-print":{"date-parts":[[1987,9]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>A simple general equation is presented for estimating the Fe<jats:sup>3+<\/jats:sup> concentrations in ferromagnesian oxide and silicate minerals from microprobe analyses. The equation has been derived using stoichiometric criteria assuming that iron is the only element present with variable valency and that oxygen is the only anion. In general, the number of Fe<jats:sup>3+<\/jats:sup> ions per <jats:italic>X<\/jats:italic> oxygens in the mineral formula, <jats:italic>F<\/jats:italic>, is given by;<\/jats:p><jats:p><jats:disp-formula><jats:graphic xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" mime-subtype=\"png\" xlink:href=\"S0026461X00021769_equ01.png\"\/><\/jats:disp-formula><\/jats:p><jats:p>where <jats:italic>T<\/jats:italic> is the ideal number of cations per formula unit, and <jats:italic>S<\/jats:italic> is the observed cation total per <jats:italic>X<\/jats:italic> oxygens calculated assuming all iron to be Fe<jats:sup>2+<\/jats:sup>. Minerals for which this equation is appropriate include pyralspite and ugrandite garnet, aluminate spinel, magnetite, pyroxene, sapphirine and ilmenite. The equation cannot be used for minerals with cation vacancies (e.g. micas, maghemite) unless, as in the case of amphiboles, the number of ions of a subset of elements in the formula can be fixed. Variants of the above equation are presented for some of the numerous published schemes for the recalculation of amphibole formulae. The equation is also inappropriate for minerals showing Si<jats:sup>4+<\/jats:sup> = 4H<jats:sup>+<\/jats:sup> substitution (e.g. staurolite, hydrogarnet), minerals containing an unknown proportion of an unanalysed element other than oxygen (e.g. boron-bearing kornerupine) and minerals containing two or more elements with variable valency.<\/jats:p>","DOI":"10.1180\/minmag.1987.051.361.10","type":"journal-article","created":{"date-parts":[[2006,12,7]],"date-time":"2006-12-07T09:54:47Z","timestamp":1165485287000},"page":"431-435","source":"Crossref","is-referenced-by-count":1472,"title":["A general equation for estimating Fe<sup>3+<\/sup> concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria"],"prefix":"10.1180","volume":"51","author":[{"given":"G. T. R.","family":"Droop","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"7149","published-online":{"date-parts":[[2018,7,5]]},"reference":[{"key":"S0026461X00021769_ref295","doi-asserted-by":"publisher","DOI":"10.1007\/BF01167213"},{"key":"S0026461X00021769_ref303","unstructured":"Spear, F.S. , Schumacher, J.C. , Laird, J. , Klein, C. , Evans, B.W. , and Doolan, B.L. (1982) Phase relations of metamorphic amphiboles: natural occurrence and theory. Ibid. 9B Amphiboles: Petrology and experimental phase relations(D. R. Veblen and P. H. Ribbe, eds.) 1-227."},{"key":"S0026461X00021769_ref298","doi-asserted-by":"publisher","DOI":"10.1515\/9781501508622-007"},{"key":"S0026461X00021769_ref292","unstructured":"Carmichael, I.S.E. (1967) The iron-titanium oxides of salic volcanic rocks and their associated ferromagnesian silicates. Ibid. 14, 36-64."},{"key":"S0026461X00021769_ref304","doi-asserted-by":"publisher","DOI":"10.1093\/petrology\/13.1.99"},{"key":"S0026461X00021769_ref290","doi-asserted-by":"publisher","DOI":"10.1086\/627358"},{"key":"S0026461X00021769_ref293","first-page":"102","volume":"64","author":"Carpenter","year":"1979","journal-title":"Am. Mineral"},{"key":"S0026461X00021769_ref297","first-page":"477","volume":"68","author":"Lindsley","year":"1983","journal-title":"Am. Mineral"},{"key":"S0026461X00021769_ref302","doi-asserted-by":"publisher","DOI":"10.1515\/9781501508257-013"},{"key":"S0026461X00021769_ref306","doi-asserted-by":"publisher","DOI":"10.1093\/petrology\/3.3.342"},{"key":"S0026461X00021769_ref294","unstructured":"Cawthorn, R.G. , and Collerson, K.D. (1974) The recalculation of pyroxene end-member parameters and the estimation of ferrous and ferric iron content from electron microprobe analyses. Ibid. 59, 1203-8."},{"key":"S0026461X00021769_ref291","doi-asserted-by":"publisher","DOI":"10.1007\/BF00371882"},{"key":"S0026461X00021769_ref296","doi-asserted-by":"publisher","DOI":"10.1007\/BF01164519"},{"key":"S0026461X00021769_ref300","doi-asserted-by":"publisher","DOI":"10.1093\/petrology\/9.3.467"},{"key":"S0026461X00021769_ref301","volume":"18","author":"Rick wood","year":"1968","journal-title":"Contrib. Mineral. Petrol"},{"key":"S0026461X00021769_ref299","unstructured":"Papike, J.J. , Cameron, K.L. , and Baldwin, K. (1974) Amphiboles and pyroxenes: characterisation of other than quadrilateral components and estimates of ferric iron from microprobe data. G.S.A. Abstracts with Programs, 6,1035-5. (abs.)"},{"key":"S0026461X00021769_ref305","first-page":"883","volume":"49","author":"White","year":"1964","journal-title":"Am. Mineral"}],"container-title":["Mineralogical Magazine"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.cambridge.org\/core\/services\/aop-cambridge-core\/content\/view\/S0026461X00021769","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2021,2,5]],"date-time":"2021-02-05T02:08:46Z","timestamp":1612490926000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.cambridge.org\/core\/product\/identifier\/S0026461X00021769\/type\/journal_article"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1987,9]]},"references-count":17,"journal-issue":{"issue":"361","published-print":{"date-parts":[[1987,9]]}},"alternative-id":["S0026461X00021769"],"URL":"https:\/\/doi.org\/10.1180\/minmag.1987.051.361.10","relation":{},"ISSN":["0026-461X","1471-8022"],"issn-type":[{"value":"0026-461X","type":"print"},{"value":"1471-8022","type":"electronic"}],"subject":[],"published":{"date-parts":[[1987,9]]}}}