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The old mineral name uralite is at times applied to an alteration product of primary pyroxene by a mixture composed largely of actinolite. The metamorphosed gabbro or diabase rock bodies, referred to as epidiorite, contain a considerable amount of this uralitic alteration.


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Fibrous actinolite is one of the six recognised types of asbestos, the fibres being so small that they can enter the lungs and damage the alveoli. Actinolite asbestos was once mined along Jones Creek at Gundagai, Australia.

Another gem variety is the chatoyant form known as cat's-eye actinolite. This stone is translucent to opaque, and green to yellowish green color. This variety has had the misnomer jade cat's-eye. Transparent actinolite is rare and is faceted for gem collectors. Major sources for these forms of actinolite are Taiwan and Canada. Other sources are Madagascar, Tanzania, and the United States.[5]

The needle-like appearance means actinolite asbestos are sharp. The sharpness of these fibers means they can puncture tissue linings and irritate the genetics of cells. When cells have genetic changes due to asbestos, they can mutate.

Actinolite is a subtype of asbestos and one of the more rare forms of the mineral. Because actinolite was not used as much as its counterparts, it is not considered a primary source of asbestos exposure. This type of asbestos is a part of the amphibole mineral family and is typically dark in color, ranging from green, black or brown.

Chrysotile, lizardite, and antigorite are the three principal serpentinesilicate minerals. Of these, only chrysotile occurs in the asbestiformhabit. Of the amphibole silicate minerals, amosite and crocidolite occuronly in the asbestiform habit, while tremolite, actinolite andanthophyllite occur in both asbestiform and non-asbestiform habits(USGS, 2001; HSE, 2005; NTP, 2005).

Talc particles are normally plate-like. These particles, when viewed onedge under the microscope in bulk samples or on air filters, may appearto be fibres, and have been misidentified as such. Talc may also formtrue mineral fibres that are asbestiform in habit. In some talcdeposits, tremolite, anthophyllite, and actinolite may occur. Talccontaining asbestiform fibres is a term that has been usedinconsistently in the literature. In some contexts, it applies to talccontaining asbestiform fibres of talc or talc intergrown on a nanoscalewith other minerals, usually anthophyllite. In other contexts, the termasbestiform talc has erroneously been used for talc products thatcontain asbestos. Similarly, the term asbestiform talc has erroneouslybeen used for talc products that contain elongated mineral fragmentsthat are not asbestiform. These differences in the use of the same termmust be considered when evaluating the literature on talc. For a moredetailed evaluation of talc not containingasbestiform fibres, refer to the previous IARCMonograph (IARC,2010).

The previous IARC Monographs were limited to the samesix commercial forms of asbestos fibres (chrysotile, actinolite,amosite, anthophyllite crocidolite and tremolite) that are subject ofthis current evaluation. In the previous IARC Monograph(IARC, 1977), theepidemiological evidence showed a high incidence of lung cancer amongworkers exposed to chrysotile, amosite, anthophyllite, and with mixedfibres containing crocidolite, and tremolite. Pleural and peritonealmesotheliomas were reported to be associated with occupational exposuresto crocidolite, amosite, and chrysotile. Gastrointestinal tract cancerswere reported to have been demonstrated in groups occupationally exposedto amosite, chrysotile or mixed fibres containing chrysotile. An excessof cancer of the larynx in occupationally exposed individuals was alsonoted. Finally the Monograph points out thatmesothelioma may occur among individuals living in neighbourhoods ofasbestos factories and crocidolite mines, and in persons living withasbestos workers.

Asbestos is a collective name for six different types of fibres:chrysotile, crocidolite, amosite, anthophyllite, tremolite, actinolite(see Section 1). Dusts from various deposits of the same type ofasbestos can cause variations in the severity of the effects observed.Erionite is a fibrous zeolite found in Central Anatolia (Turkey), andOregon (USA) (see Section 1 of the Monograph onErionite). Talc is a hydrated magnesium silicate, and talc ore maycontain several other minerals including anthophyllite, tremolite,calcite, dolomite, magnesite, antigorite, quartz, pyrophyllite micas, orchlorites (see Section 1).

Asbestos minerals can be divided into two groups: serpentineasbestos (chrysotile[Mg3Si2O5(OH)4]),and amphibole asbestos (crocidolite[Na2(Mg,Fe2+)3Fe23+Si8O22(OH)2],amosite[(Mg,Fe2+)7Si8O22(OH)2],tremolite[Ca2Mg5Si8O22(OH)2],actinolite[Ca2(Mg,Fe2+)5Si8O22(OH)2],and anthophyllite[Mg7Si8O22(OH)2]).Formulae reported are ideal and are always significantlymodified in nature by the occurrence of several substitutingcations (e.g. Fe2+/3+, Al3+,Na+). The crystal structure of chrysotile resultsfrom the association of a tetrahedral silicate sheet ofcomposition(Si2O5)n2n- withan octahedral brucite-like sheet of composition[Mg3O2(OH)4]n2n+,in which iron substitutes for magnesium. The two sheets arebonded to form a 1:1 layer silicate; a slight misfit between thesheets causes curling to form concentric cylinders, with thebrucite-like layer on the outside. Van der Waals interparticleforces hold together fibrils into the actual fibre so that, whenchrysotile breaks up, a large number of smaller fibres orfibrils are generated (Fubini & Otero Areán, 1999).

There is sufficientevidence in humans for the carcinogenicity of all forms ofasbestos (chrysotile, crocidolite, amosite, tremolite, actinolite, andanthophyllite). Asbestos causes mesothelioma and cancer of the lung, larynx,and ovary. Also positive associations have been observed between exposure toall forms of asbestos and cancer of the pharynx, stomach, and colorectum.For cancer of the colorectum, the Working Group was evenly divided as towhether the evidence was strong enough to warrant classification assufficient.

Actinolite is a member of a series that contains varying amounts of iron and magnesium. Tremolite is the Mg end, and ferroactinolite the Fe end, with actinolite in the middle. Actinolites with more than 50% Fe are very rare. Catseye actinolite exists (S.G. 3.0, R.I. 1.63); when chatoyant material is cut, it exhibits a fine eye. Actinolite is easy to cleave and hard to cut and would make a poor jewelry stone. Actinolite is the chief constituent of nephrite (jade). Smaragdite is a chrome-rich tremolite from Tanzania.

Hornblende-Actinolite Occurrence and Compositon Hornblende and actinolite are both amphiboles. Hornblende is a widespread and common mineral in many types of igneous and metamorphic rocks. Actinolite is found in metamorphosed mafic to intermediate rocks.

Important properties Color - Hornblende is generally pleochroic in shades of brown and green, less commonly yellow or red-brown. Concentric or patchy color zonation may be present. Actinolite is similar but colors are restricted to greens. Cleavage - Amphiboles have diagnostic 60o-120o cleavage angles when viewed in end section. Other views may show only one cleavage. Interference colors - Maximum interference colors are middle second order but they may be masked by the color of the mineral. Form - Often sub- to anhedral but may be prismatic crystals forming lathes. End views may show diamond shaped cross-sections. Interference figure - Hornblende and actinolite are biaxial (-) with a large 2V.

The photos above show mostly the pleochroic green amphibole actinolite and clear quartz (PP). Also present is black opaque magnetite. In the XP view, the deep color of the actinolite partially masks the interference colors, making them somewhat anomalous. A few of the amphibole grains show the classic 60o-120o cleavage angles.

Reflectance spectra of medium (0.005 μm between 0.3 and 2.7 μm) and high (0.0002 μm between 1.38 and 1.42 μm and 0.002 μm between 2.2 and 2.5 μm) spectral resolution of 19 minerals from the tremolite-actinolite solid solution series are used to characteiue systematic variations in absorption band parameters as a function of composition. The medium-resolution data are used to characterize broad absorptions associated with electronic processes in Fe3+ and Fe2+, and the high-resolution data are used to characterize overtones of OH vibrational bands. Quantitative analyses of these data were approached using a model that treats absorptions as modified Gaussian distributions (Sunshine et al., 1990). Each spectrum was deconvolved into a set of additive model absorption bands superimposed on a reflectance continuum. For absorptions associated with electronic processes, the model bands were shown to provide estimates of the Fe and Mg mineral chemistry with correlations of greater than 0.98. The systematic changes in the energy, width, intensity, and number of OH overtone bands are easily quantified using the modified Gaussian model, and the results are highly correlated with the Fe/Mg ratios of the samples. These results indicate that the modified Gaussian model can be used to quantify objectively the bulk chemistry of the minerals of the tremolite-actinolite solid solution series using high-resolution reflectance spectra of the OH overtone bands.

The term cat's eye, or chatoyancy, is used to describe a phenomenal optical property in gemstones, in this case actinolite. The effect, when present, appears as a bright, narrow slit similar to the pupils in the eyes of your favorite feline. This phenomenon is caused by parallel fibrous or needle-like inclusions that interfere with the passage of light throughout the crystal, scattering and reflecting light back to the viewer as a thin line.

This actinolite sample shows a formation pattern somewhat similar to the above, but very different from the fibrous form below. This sample is formed after pyroxene. It is about 20x16 cm and is from Calumet mine, Salida, Colorado. 041b061a72

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