The International Mineralogical Association's approved amphibole nomenclature has been revised in order to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely and include new amphibole species discovered and named since 1978, when the previous scheme was approved. The same reference axes form the basis of the new scheme and most names are little changed but compound species names like tremolitic hornblende (now magnesiohornblende) are abolished and also crossite (now glaucophane or ferroglaucophane or magnesioriebeckite or riebeckite), tirodite (now manganocummingtonite) and dannemorite (now manganogrunerite). The 50% rule has been broken only to retain tremolite and actinolite as in the 1978 scheme so the sodic calcic amphibole range has therefore been expanded. Alkali amphiboles are now sodic amphiboles. The use of hyphens is defined. New amphibole names approved since 1978 include nyböite, leakeite, kornite, ungarettiite, sadanagaite and cannilloite. All abandoned names are listed. The formulae and source of the amphibole end member names are listed and procedures outlined to calculate Fe3+ and Fe2+ when not determined by analysis.

The International Mineralogical Association's approved amphibole nomenclature has been revised in order to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely, and include new species of amphibole discovered and named since 1978, when the previous scheme was approved. The same reference axes form the basis of the new scheme, and most names are little changed, but compound species names like tremolitic hornblende (now magnesiohornblende) are abolished, as are crossite (now glaucophane or ferroglaucophane or magnesioriebeckite or riebeckite), tirodite (now manganocummingtonite) and dannemorite (now manganogrunerite). The 50% rule has been broken only to retain tremolite and actinolite as in the 1978 scheme; the sodic-calcic amphibole range has therefore been expanded. Alkali amphiboles are now sodic amphiboles. The use of hyphens is defined. New amphibole names approved since 1978 include nyböite, leakeite, kornite, ungarettiite, sadanagaite and cannilloite. All abandoned names are listed. The formulae and source of the amphibole end-member names are listed, and procedures outlined to calculate Fe 3+ and Fe 2+ where not determined by analysis.

Contents 1. General classification of the amphiboles 2. The iron-magnesium-manganese amphiboles 3. The calcic amphiboles 4. The sodic-calcic amphiboles 5. The alkali amphiboles 6. Formulation of individual proposals as approved by the Commission 7. Amphibole names to be abandoned Errata (l) In Fig. I, the point labelled 0.67 Nas along the (3) p. 10a5, 14.12: NaCaNa not NaCaNao left-hand back edge should be 1.34 Na'.

GENsneL Cr-essrrcanoN oF THE Ar"tprnnorrs It is proposed that the classification of the amphiboles should be largely based on crystal chemistry, as the optical and other physical determinative properties such as X-ray powder diffraction cannot differentiate unambiguously between different members of the group. Of course the traditional and important distinction between orthorhombic and monoclinic members has been retained. When it is necessary to distinguish different polytypes or polymorphs further (e.9., with cummingtonite) this may be *Final report by the subcommittee on the Amphtbole Group as approved by tho International Mineralogical Association Commission on New Minerals and Mineral Names. The amphibole subcommittee was composed of H. Winchell, Chairman (J.S.A.), R. A. Binns (Australia), M. Fleischer (U.S.A.) later replaced by A. Kato (Japan), C. Guillemin (France) later replaced by G. Gottardi (Italy), M. Fonteilles (France), E. Hilmy (ECypt), B. E. kake ru.K.), K. f. Neuvonen (Finland), and L. van der Plas CIhe Netherlands) later replaced by H. J. Kisch (Israel). All the reports were compiled by B. E. kake.

The introduction of a fifth amphibole group, the Na-Ca-Mg-Fe-Mn-Li group, defined by 0.50 < B(Mg,Fe2+,Mn2+,Li) < 1.50 and 0.50 ≤ B(Ca,Na) ≤ 1.50 a.f.p.u. (atoms per formula unit), with members whittakerite and ottoliniite, has been required by recent discoveries of B(LiNa) amphiboles. This, and other new discoveries, such as sodicpedrizite (which, here, is changed slightly, but significantly, from the original idealized formula), necessitate amendments to the IMA 1997 definitions of the Mg-Fe-Mn-Li, calcic, sodic-calcic and sodic groups. The discovery of obertiite and the finding of an incompatibility in the IMA 1997 subdivision of the sodic group, requires further amendments within the sodic group. All these changes, which have IMA approval, are summarized.