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Igneous Rocks
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
Quartz, alkali feldspar, a smaller amount of plagioclase, and mica are essential constituents; in some rocks microcline is present. The feldspar may form up to 50% of the rock; the mica is biotite or muscovite, or both. Other minerals found in some granites include hornblende and tourmaline; alkaline types of granite may have Na-rich minerals such as aegirite and riebeckite. Accessory minerals are apatite, magnetite, sphene, zircon, and occasionally garnet (Fig. 5.23).
Petrography of martite–goethite ore and implications for ore genesis, South Flank, Hamersley Province, Western Australia
Published in Australian Journal of Earth Sciences, 2021
Quartz, carbonate and silicate phases make up significant proportions of certain BIF laminae. The carbonate phases most common in fresh BIF macrobands of the MMIF range in composition between ferroan dolomite and magnesian ankerite. These carbonates occur dominantly as relatively coarse-grained porpyroblasts (<800 µm in diameter), which range in shape from subhedral to euhedral and rhombic. Carbonate grains are commonly zoned, with a clear rim surrounding a core rich in inclusions. The dominant Fe-silicate phases are minnesotaite, stilpnomelane and riebeckite. Minnesotaite, which occurs as sprays and sheaves, typically forming ‘bow-ties’ that coalesce as the percentage increases to give a felted appearance, is present in many assemblages but is always closely associated with chert. Ferroan talc is also commonly present and has a more bladed habit compared with the acicular habit of minnesotaite. Riebeckite is commonly present in the Mt Newman Member (although not as a major constituent) and chlorite and greenalite are rare constituents. Trace amounts of apatite and sulfide are present. The statistical analysis of Morris (1991) reveals a very strong association between magnetite and quartz. Riebeckite and talc are moderately associated with quartz–magnetite layers, and siderite and minnesotaite are weakly associated.
Characterization of pulmonary responses in mice to asbestos/asbestiform fibers using gene expression profiles
Published in Journal of Toxicology and Environmental Health, Part A, 2018
Naveena Yanamala, Elena R. Kisin, Dmitriy W. Gutkin, Michael R. Shurin, Martin Harper, Anna A. Shvedova
Asbestos is a term for a set of commercially important naturally occurring fibrous silicate minerals. Crocidolite (asbestiform riebeckite), amosite (asbestiform cummingtonite-grunerite), actinolite-tremolite asbestos, and anthophyllite asbestos belong to the amphibole minerals, while chrysotile is a serpentine mineral (Wylie and Candela 2015). The term “asbestiform” corresponds to a mineralogical habit or form of a mineral in which single fibers (fibrils) occur in bundles that can be detached into finer fibers and display curvature (Lowers and Meeker 2002). Similar to main asbestos types described above, there are “other regulated asbestiform minerals” fibers such as durable asbestiform zeolite minerals (e.g., erionite). The term asbestos has been used in commerce and regulations, but is not recognized in geology as referring to species separate from non-asbestos analogs of these minerals (Lowers and Meeker 2002). These materials were widely used for textiles and in construction, as well as in industrial application, until the 1970’s in the USA (Williams, Phelka, and Paustenbach 2007). Although the use has declined, asbestos continues to be utilized for certain applications in the USA and elsewhere (Dodson 2016; LaDou et al. 2010). Known human diseases associated with exposure to asbestos/asbestiform fibers include asbestosis, bronchial adenocarcinoma, squamous cell carcinoma of the respiratory epithelium and large/small cell lung carcinoma and diffuse malignant mesothelioma (Andujar et al. 2016; Lemen 2016; Ndlovu et al. 2017).