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Metamorphic Rocks
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
Many metamorphic rocks are bimodal, meaning they contain mineral crystals of two sizes. Such rocks, termed porphyroblastic rocks, contain large crystals that have grown within a sea of finer-grained mineral material. The large crystals, called porphyroblasts, may be anhedral but are often subhedral or euhedral. The finer material is the groundmass. Some of the most spectacular porphyroblastic rocks are mica-rich schists that contain chloritoid, kyanite, garnet, or staurolite as porphyroblasts. Figure 10.6 shows a schist from southern Switzerland, near Italy, that contains porphyroblasts of kyanite (blue) and staurolite (brown). The largest of the blue kyanite blades are about 4 cm long. In this rock, a silvery mica called paragonite constitutes most of the groundmass. Figure 10.7 shows garnet in an outcrop on Syros, one of the western Greek islands. The largest of the porphyroblasts are about 2 cm across. The groundmass in this rock is mostly quartz and feldspar with lesser amounts of biotite. Garnet is a very common porphyroblast in rocks that metamorphose at medium to high temperature, and garnet crystals are commonly euhedral to subhedral, like the crystals shown here.
Beneficiation of lithium bearing pegmatite rock: a review
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Saroj Kumar Sahoo, Sunil Kumar Tripathy, A. Nayak, K. C. Hembrom, S. Dey, R. K. Rath, M. K. Mohanta
The unit structure of lepidolite is one octahedral sheet (Os) sandwiched between two opposing tetrahedral sheets (Ts), forming a layer separated by planes of non-hydrated interlayer cations (I) (Rieder et al. 1999). Lepidolite is designated as incompletely investigated trioctahedral mica on or close to the trilithionite-polylithionite crystallizing in the monoclinic system (Rieder et al. 1999). Lepidolite is essentially confined to granite pegmatites, where it is associated with quartz, microcline, albite, and common pegmatites accessories tourmaline, topaz, beryl, and lithium minerals. Lepidolite is occasionally reported in granites and hypothermal veins with cassiterite. It usually has lower relative indices than muscovite or paragonite, and its occurrence is somewhat distinctive. Natural lepidolite may contain up to 98% polylithionite, 60% paucilithonite, and 3.5% muscovite. Mn+2, Fe+2, Fe+3, and Mg+2 may enter octahedral coordination with Li+3, and Al+3 and manganese may be present in very significant amounts (Phillips and Griffen 1981). Lepidolite often contains significant amounts of Rb+, Cs+, and Na+ as a substitute for K+ and traces of many other elements have been noted as octahedral/Interlayer cations, so it is considered a source of rubidium also (Tadesse et al. 2019; Wietelmann and Steinbild 2000). Lepidolite is associated with calcite, feldspar, mica, and quartz as the major gangue minerals (Bulatovic 2014).
Surface and volume crystallization in fluorrichterite based glasses
Published in Journal of Asian Ceramic Societies, 2020
R. Casasola, J. M. Pérez, M. Romero
Figure 7 shows the X-ray pattern from R10 glass after heat treatment at 850°C for 5 min. The profile of the diffractogram indicates that after this treatment, the glass is in an initial state of its devitrification process, as is deduced by the presence of a high amorphous background on which wide peaks of crystallization overhang. X-ray pattern can be associated with the occurrence of preiswerkite (NaMg2Al(Si2Al2)O10F2) and paragonite (NaAl2(Si3Al)O10F2) crystalline phases, both belonging to the mica group. However, semi-quantitative EDS analyses performed on the crystals of Figure 6 does not completely match the identified micas. The chemical composition of the micas is extremely variable and numerous homo- and heterovalent isomorphic mixtures are recorded. In the case of R10 glass, these substitutions are also favored by the glass composition itself, which is scarce in alumina and it is no able to deal with the requirement of Al3+ cations necessary for the development of mica crystals. In this sense, Veblen [30] reported new ordered structures, called biopyriboles, which are intimately related to amphiboles. This term, derived from biotite, pyroxene, and amphibole, reflects the connection between these mineralogical phases.
Predicting the antagonistic effect between albite-anorthite synergy and anhydrite on chemical enhanced oil recovery: effect of inorganic ions and scaling
Published in Journal of Dispersion Science and Technology, 2020
Eric O. Ansah, Ronald Nguele, Yuchi Sugai, Kyuro Sasaki
Hence, in the oil -NaCl water-feldspar system, K-feldspar was leached extensively to form amorphous minerals, possibly paragonite and the further reaction proceeded to albite precipitation. Also, the K-feldspar was replaced by albite with a direct substitute of K+ by Na+ in the system with high ratios of Na+/K+. Per this research, considering the above mentioned antagonistic effect of feldspar dissolution effects on CEOR has proven the feasibility of injecting ex situ generated ME into a reservoir to recover oil. In that, as shown herein backed by our experimental data, the scaled mineral, albite and silica precipitate (amorphous/gel) formed during production, easily dissolves comparing carbonate precipitates.