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Semi-precious stones
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Spessartine or spessartite is manganese aluminium garnet Mn3Al2(SiO4)3. It is often found in granite pegmatite and allied rock types and in certain low grade metamorphic phyllites.
3D simulations for the Brenner Base Tunnel considering interaction effects
Published in Daniele Peila, Giulia Viggiani, Tarcisio Celestino, Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2020
The Innsbruck Quartzphyllite consists mainly of quartz-rich phyllites (quartzphyllites), mica and quartzite schists with greenschist, marble, orthogneiss and graphite phyllite inclusions. From a volumetric point of view, the most important minerals are quartzite, mica and chlorite in varying proportions with the addition of feldspar, resulting in phyllite, quartz phyllite, micaschists and quartzite schists, c.f. Bergmeister & Töchterle (2013).
Minerals, rocks, discontinuities and rock mass
Published in Ömer Aydan, Rock Mechanics and Rock Engineering, 2019
Phyllite was originally a fine-grained sedimentary rock such as sandy mudstone or shale composed mainly of clay minerals in a semirandom orientation. Phyllite is a common metamorphic rock, formed under a low-heat and high-pressure environment.
Oxidised gold lode stains black: the historical Encardideira (Chico Rei) deposit, Ouro Preto, Brazil
Published in Applied Earth Science, 2023
A. R. Cabral, L. P. T. Nazareth, L. C. da Silva, L. E. D. Amorim, A. F. Amorim, I. L. F. Ferreira, M. H. S. Franco, M. C. R. Gomes, P. R. Lage Ferreira, M. M. Marques, N. C. S. Martins, I. Mendes de Oliveira, S. D. Veiga, G. V. Terenzi, F. J. Rios
Four out of five samples returned Au values between 1.2 and 24.0 ppm (Table 1). The sample of soft reddish phyllite gave 2.0 ppm Au. The latter has the highest contents of Al2O3 (16.5%), K2O (3.5%), MgO (0.9%) and graphite C (3.0%) of the sample set. The soft reddish phyllite also has remarkable total contents of Fe and Mn, given as Fe2O3 and MnO of 12.3% and 6.9%, respectively. Such a chemical composition is mineralogically expressed as muscovite, goethite and pyrolusite. The rock is a quartz–muscovite phyllite where quartz occurs as foliation-forming ribbons. Muscovite is the main mineral that defines the pervasive foliation of the phyllite. Its foliation is truncated at low angle by pockets of goethite pseudomorphs after a sulfide mineral (Figure 3(a)), the triangular prismatic habit of which indicates arsenopyrite (Figure 3(b)). A further indication for pre-existing arsenopyrite is the whole-rock enrichment in As and, subordinately, Ni (0.37% As, 1344 ppm Ni, Table 1 – n.b. the Passagem de Mariana arsenopyrite has Ni contents of up to 828 ppm, Cabral and Koglin 2012). Pyrolusite forms pockets that are spread over the foliation (Figure 3(c,d)), but graphite, as expected from the content of graphite C, went unrecognised in the reddish quartz–muscovite phyllite.
Characterization of hydro chemistry and groundwater quality evaluation for drinking purpose in Adigrat area, Tigray, northern Ethiopia
Published in Water Science, 2018
The Metamorphic Rock unit is exposed in the eastern part of the area that has both volcanic and sedimentary origins. This rock unit is inhomogeneous Phyllite, slate and volcanic rocks as well as gray wacky deposited. The slate is very fine gained in texture, dark gray in color and has perfect slaty cleavage. The Phyllite on the other hand is pinkish to whitish in color, fine to medium grained, shiny and has soapy appearance. The metavolcanic clast/metavolcanic rock are massive poorly to moderately foliate. It is light greenish in color; probably derived from intermediate magma and bears quartz veins and vein-lets (Ermias et al., 2015).