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Minerals
Published in Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough, Earth Materials, 2019
Dexter Perkins, Kevin R. Henke, Adam C. Simon, Lance D. Yarbrough
Some rocks contain only one kind of mineral. Limestone (a sedimentary rock), for example, is often pure calcite (mineral). Dunite, an igneous rock that crystallizes from magma, is often nearly 100% olivine (mineral). Other rocks are composed of multiple minerals and generally named based on mineral proportions. Thus, all granite (rock), for example, contains subequal amounts of quartz (mineral) and alkali feldspar (mineral), often with lesser amounts of plagioclase (mineral).
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
Olivine is the chief constituent of peridotite (from French peridot, olivine); other minerals include pyroxene, hornblende, biotite, and iron oxides. Felsic minerals are absent. A variety composed almost entirely of olivine is called dunite, from the Dun Mountain, New Zealand; pale green in colour, it has been used as a decorative stone on a small scale.
Tectonic setting and mineralisation potential of the Cowley Ophiolite Complex, north Queensland
Published in Australian Journal of Earth Sciences, 2022
A. Edgar, I. V. Sanislav, P. H. G. M. Dirks
The ultramafic rocks observed within the COC are comparable with the bedrock lithologies that have been described from the Greenvale Ni–Co–Sc–Cr laterite deposits (Zeissink, 1969). Sc in ultramafic rocks is primarily hosted within clinopyroxene (Williams-Jones & Vasyukova, 2018). Consequently, pyroxenite has been recognised as a favourable host rock to primary, magmatic Sc mineralisation and secondary, laterite-hosted Sc mineralisation (Wang et al., 2021). Ni laterite deposits are developed best on top of harzburgite and dunite. Ni preferentially partitions into olivine during the fractionation of ferro-magnesian magmas (Herzberg et al., 2016); thus, olivine-rich peridotite generally contains greater concentrations of Ni. We have interpreted that, prior to alteration, the COC comprised differentiated peridotite, including pyroxenite and dunite. The COC contained bedrock lithologies that were favourable to the formation of lateritic Ni–Co–Sc–Cr deposits; however, we have not observed evidence for the development of a thick laterite profile in which leached metals could be concentrated into economically viable lodes.
Study of the kinetics of the magnesium leaching from serpentine bearing chromite overburden rocks for mineral carbonation
Published in Mineral Processing and Extractive Metallurgy, 2020
Veerendra Singh, Rajat Rautela, Krishna Sandilya Durbha, Y Rama Murthy
Chromite ore resources in the world are commonly found associated with magnesium bearing mafic and ultramafic rocks (Gu and Wills 1988). In Sukinda belt, India, chromite is present in the layers of rocks. The overburden rock is composed of the ultramafic rocks, such as dunite, peridotite and their altered products (serpentinite), pyroxenite and saxonite. The major minerals present are olivine (Mg2+,Fe2+)2SiO4, orthopyroxenes (MgSiO3-(Mg,Fe)SiO3), diopside (MgCaSi2O6) (Mohanty et al. 2009). During mining of chromite ores these rocks are mined and stored as waste material around the mining site. Huge dumps of waste material in the mining site has been created and need additional care to avoid land slide and other environment threats. Researchers are working in this area to explore suitable application of these waste dumps. Mohanty et al. proposed wide application of serpentine mineral bearing waste rocks with reference to iron and steel industry (Mohanty et al. 2009). The other applications such as mineral carbonation, magnesium metal recovery, etc. Are also being explored by other researchers (Park and Fan 2004; Ficara et al. 1998). This study is carried out to understand leaching behaviour of magnesium bearing overburden rocks and their possible application for mineral carbonation to develop an integrated environmental friendly method for ferroalloy production.
Emplacement and Paleozoic and Cretaceous recrystallisation of the Broughton Arm Peridotite in Western Fiordland, New Zealand
Published in New Zealand Journal of Geology and Geophysics, 2019
T. Dwight, J. M. Scott, J. J. Schwartz
The Broughton Arm Peridotite adds to the growing database of ultramafic rocks in New Zealand. Composed of several variably metamorphosed and recrystallised rocks outcropping over an area of 500 m (although it may extend several km to the north), it provides a record of the complex igneous and metamorphic history of central Fiordland from the mid-Paleozoic to the Cretaceous. The protolith to the Broughton Arm Peridotite is most likely to have been an ultramafic cumulate magma emplaced in the early to mid Paleozoic. A first metamorphic event, probably in the Carboniferous at c. 330 Ma, formed olivine–enstatite–Cr magnetite-dominated dunite and harzburgite assemblages. The margins of the peridotite have been subsequently converted to near mono-mineralic hornblendite and then amphibolite, and the harzburgitic-dunitic core has partially recrystallised to Mg-chlorite, tremolite, serpentinite-dominated assemblages. The growth of the hydrous phases was associated with grain size reduction, and in-situ titanite U-Pb dating of deformed host gneisses indicates that this amphibolite facies assemblage formed c. 106 Ma concurrent with deformation along the extensional Doubtful Sound Shear Zone.