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Precious stones
Published in Francis P. Gudyanga, Minerals in Africa, 2020
Emerald is a cyclosilicate green [943] variety of the mineral beryl Be3Al2(SiO3)6 which has a green colour because of the inclusions of trace elements of chromium and vanadium [942]. There is a tendency of emeralds having numerous inclusions and surface-breaking fissures [886] which are imperfections unique to each emerald and can be used to identify a particular stone.
Plutonic 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
Pegmatites are also sources of spectacular mineral specimens that grace museum collections. The 11-centimeter-tall emerald crystals in Figure 6.17 are on display at the Smithsonian National Museum of Natural History in Washington, DC. Emerald is a variety of beryl, and this specimen contains some of the most beautiful and perfectly formed beryl crystals in the world. The specimen was collected in 1971 from a pegmatite near Stony Point, North Carolina.
Atomic and Molecular Origins of Color
Published in Mary Anne White, Physical Properties of Materials, 2018
Interestingly, emeralds, which are green, also derive their color from Cr3+ ions, this time in a material with composition Be3Al2SiO6 (known as beryl when pure). The Cr3+ in this structure is in a very similar environment to that in ruby, but it experiences a different crystal field strength. The difference in color subtly illustrates the importance of the magnitude of the crystal field strength. Determination of whether the crystal field strength is less than or greater than in ruby is left as an exercise for the reader.
Lithium in pegmatites of the Fennoscandian Shield and operation prospects for the Kolmozero deposit on the Kola Peninsula (Russia)
Published in Applied Earth Science, 2022
P. V. Pripachkin, N. M. Kudryashov, T. V. Rundkvist, L. N. Morozova
Albite-spodumene pegmatites are leucocratic rocks exhibiting a zoned structure changing from the fine-grained pegmatite along the contact to the pegmatitic and blocky textures in the central parts. The zone I consists of 3–5 cm thick aplitic rim of the quartz-plagioclase composition developed at the contact of pegmatites with metagabbro-anorthosites. Zone-II incudes medium-grained quartz-muscovite-feldspar pegmatites containing the light-blue to green apatite and pink-brown spessartine. The zone is narrow, the thickness commonly less than 30 cm and discontinuous along the strike. The zone III is the largest and encompasses up to 85–90% of the vein volumes. It is composed of coarse-grained quartz-spodumene-feldspar pegmatite with beryl, columbite, tantalite and contains the giant, up to 1.5 m long, crystals of greenish spodumene. This zone also shows areas of blocky microcline and quartz; however, the quartz core was observed in one vein only. Lithium grade changes from the marginal zone of the pegmatites to the central parts of the veins, increasing from 0.1 wt.-% of Li2O to 2.55 wt.-% of Li2O (Table 2). The increase of the lithium grade is coupled with a decrease of the fractionation index (the Mg/Li ratio (Table 2), which drops from 1.04 at the marginal parts of the pegmatites to 0.04 at the centre (Morozova 2018).
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).
Extraction equilibrium conditions of beryllium and aluminium from a beryl ore for optimal industrial beryllium compound production
Published in Canadian Metallurgical Quarterly, 2019
Alafara A. Baba, Daud T. Olaoluwa, Ayo F. Balogun, Abdullah S. Ibrahim, Fausat T. Olasinde, Folahan A. Adekola, Malay K. Ghosh
Beryllium metal, alloys and some compounds of beryllium especially beryllium sulphate have been used widely in industry for many decades particularly in specific areas of nuclear technology. Their ability to reflect neutrons and its efficiency in the production of neutrons when exposed to alpha emitters has led to its use in nuclear reactors and nuclear weapons [1,2]. These applications have the impetus to the development in its extraction and manufacturing processes through different routes. The production of beryllium from beryl ore is a complicated process because of the inert nature of the mineral with mineral acids under the normal conditions of temperature and pressure. Therefore, leaching of beryllium from the mineral is generally carried out by fusion with potassium hydroxide and potassium carbonate mixture, followed by quenching in cold water to destroy the original crystal structure of beryl [3]. The soluble alkali salts are dissolved in water and the glassy beryl is reheated, ground and dissolved with a sulphuric acid solution [4]. This solution contains mainly aluminium together with beryllium and other impurities. To this solution, ammonia liquor is added to precipitate beryllium hydroxide and bring most of the ammonium alum in solution.