On the Classification of Amphiboles

Abstract

Major issues involved in the classifi cation of the amphiboles are examined: (1) the role of (OH), Li and Fe 3+ , (2) the formal defi nition of a root name, (3) irreducible charge-arrangements and distinct species, (4) the use of prefi xes, (5) the principal chemical variables used in a classifi cation procedure, and (6) the use of the dominant-constituent principle. The current IMAapproved classifi cation scheme is based on the A, B and T groups of cations in the amphibole formula: AB 2 C 5 T 8 O 22 W 2 . We argue here that classifi cation should be based on the A, B and C groups of cations as (i) it is in these groups of cations that the maximum variation in chemical composition occurs, and (ii) as a result of (i), the scheme is more in accord with the IMA-sanctioned dominant-constituent principle, which governs the recognition (and approval) of distinct mineral species. Two new classifi cations are presented here; one is based on the A, B and C groups of cations, and another on the dominant-constituent principle. These two schemes were produced to illustrate (i) the problems inherent in the classifi cation of a group of minerals as complicated as the amphiboles, and (ii) the sometimes disparate needs of crystallographer, mineralogist, petrologist and geochemist. Scheme 1 conserves current formulae and names as much as possible, whereas scheme 2 minimizes the number of formulae and names as much as possible. The differences between the current classifi cation and the two schemes presented here are discussed, and we highlight the problems associated with each scheme.Keywords: amphibole group, classifi cation. SOMMAIRENous passons en revue les aspects importants d'une classifi cation des amphiboles: (1) le rôle de (OH), Li et Fe 3+ , (2) la défi nition formelle d'un nom "racine", (3) les arrangements irréductibles des charges et le concept des espèces distinctes, (4) l'utilisation de préfi xes, (5) les variables chimiques importantes utilisées dans la procédure de classifi cation, (6) l'utilisation du principe de la composante dominante. Le schéma de classifi cation accepté présentement par l'Association Internationale de Miné-ralogie (IMA) repose sur une considération des occupants cationiques des sites A, B et T d'une amphibole, AB 2 C 5 T 8 O 22 W 2 . Nous proposons plutôt de fonder le schéma de classifi cation sur les occupants des sites A, B et C, parce que c'est parmi ces groupes de cations que se trouve la plus grande variabilité en composition chimique. De plus, cette pratique donnerait un schéma plus en accord avec le principe de la composante dominante, qui régit la distinction et l'acceptation des espèces minérales distinctes. Nous présentons deux nouvelles classifi cations; une de celles-ci est fondée sur les occupants cationiques des sites A, B et C, et une autre est fondée sur le principe de la composante dominante. Ces deux schémas ont été préparés afi n d'illustrer (i) les problèmes intrinsèques d'une classifi cation d'une groupe de minéraux aussi compliqués que les amphiboles, et (i...

New insights on the biomineralisation process developing in human lungs around inhaled asbestos fibres

“…SEM micrographs also show the inner crocidolite fibre in parts of the AB where the coating is interrupted (Figure S2 in the SI). The diameter of the fibres was measured to fall in the range between 0.3–0.4 μm, in agreement with that reported for crocidolite fibres18. Several uncoated fibres, were also detected (Fig.…”

“…. Accordingly to the type of asbestos used in the plant, EDS microanalysis of uncoated parts of the fibres (Figure S2 in the SI) allowed identifying them as crocidolite asbestos, which has ideal chemical formula NaFe 2 (Fe, Mg) 3 Si 8 O 22 (OH) 2 and contain ~27% Fe18. More detailed information on the nature of asbestos fibres from samples with the same origin can be found in a previous work51.…”

K-Ar Dating of Amphiboles from Andesite of Complex Dyke in Dubie (Southern Poland)

“…The (Hawthorne and Oberti, 2006). This identification is in agreement with the X-ray diffraction pattern (Table 1), where the amphibole main reflexes are like those of the reference magnesiohornblende (JCPDS21-0149) and slightly diverge from those of ferro-tschermakite (JCPDS43-0665).…”

Applying Definitions of “Asbestos” to Environmental and “Low-Dose” Exposure Levels and Health Effects, Particularly Malignant Mesothelioma

“…While the most useful definitions would be interdisciplinary and unchanging, it has recently been suggested that “the rigor of established mineralogical terminology is critical to the research process and the ultimate understanding of the mechanisms of toxicity” (Institute of Medicine [IOM], 2009). Inevitably though, these are anything but unchanging, particularly with respect to the classification of amphibole minerals (IOM, 2009, Leake, 1997; 2004, Hawthorne & Oberti, 2007). IOM (2009) suggested in reviewing the “NIOSH Roadmap” (IOM, 2009, NIOSH, 2010) that:…”

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