Phase transformations of ilmenite ore during microwave treatment at a frequency of 2.45 GHz under the influence of sucrose
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The present work is devoted to the influence of combined microwave heating at a frequency of 2.45 GHz on the oxidation process of Vietnamese ilmenite ore. In oxidation by this method, the heating rate is high for the first 0.5 h and decreases during subsequent treatment. In this case, in the whole volume of each ilmenite ore particle, equilibrium pseudobrookite and rutile phases form. It is shown that, under the influence of microwave irradiation, the growth rate of the pseudobrookite phase is higher than that of the rutile phase. To reduce iron contained in the obtained pseudobrookite-rutile mixture, sucrose was added to it. However, the X-ray diffraction analysis data indicate that iron is not reduced under the action of sucrose, and reverse transformation of pseudobrookite into ilmenite occurs.Keywords:
Ilmenite
Rutile
The holotype specimen of the discredited “kalkowskyn”, from Ouro Preto, Minas Gerais, Brazil, was investigated by EDS and X-ray powder diffraction. It consists of a mixture of pseudorutile, rutile, and hematite, probably generated by alteration of ilmenite. Intergrowths of rutile and hematite, with exsolution textures, were interpreted to have formed from pseudorutile. Associated minerals are quartz, almandine, muscovite, monazite-(Ce), and zircon.
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Abstract Ilmenite concentrates obtained from heavy mineral deposits in the Murray Basin, southeastern Australia contain appreciable quantities (up to 10 wt.%) of an unusual hydrated Fe titanate mineral in the form of orange to red coloured translucent grains. The grains are weakly magnetic and have a low apparent density (<3.3 g cm –3 ) due to microprosity, which enables them to be easily concentrated in a pure state. Samples from different deposits have similar analyses of 67–69% TiO 2 , 8 –9% Fe 2 O 3 , 2–3% FeO, 11 –12% H 2 O and 8 –9% of intra-pore impurities, mainly SiO 2 and Al 2 O 3 . The powder pattern for the mineral closely matches that for pseudorutile; having a hexagonal subcell with a = 2.844 (1) Å, c = 4.575 (1) Å. The idealized composition range of the Fe titanate, calculated from analyses and structure refinements, is [FeTi 6 O 12 (OH) 3 ].3H 2 O to [FeTi 6 O 11 (OH) 5 ].2H 2 O. The molecular water is nonstructural, probably adsorbed on the surfaces of nano-scale domains of the mineral. Electron microprobe and scanning electron microscopy studies provide evidence for formation of the mineral by replacement reactions acting on MgO-rich ferrian ilmenite grains. The mineral represents a distinct intermediate in the chemical weathering of ilmenite, having a pseudorutile-like structure but a leucoxene-like composition. It is unusual in not having undergone any recrystallization to phases such as rutile and anatase.
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Combined electron microprobe and scanning electron microscope (SEM) x-ray image analyses are used to obtain semiquantitative data on the relations between ilmenite grains and their exsolved chromite and rutile. Comparisons of these data for ilmenites in four Apollo-17 high-Ti basalts with a database of electron microprobe analyses from the literature indicates that Cr expulsion from ilmenite can be as important as Fe{sup 2+} reduction in causing subsolidus exsolution of chromite and rutile from ilmenite. 12 refs., 4 figs., 5 tabs.
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Fifteen beach sand samples were collected from a depth of 1mt at different locations of the Astaranga beach, Puri with an interval of 300 mts. The beach sand samples were studied for heavy mineral concentration at different location points and were subjected to scanning electron microscope studies for the mineral ilmenite. The percentage of total heavy mineral in Astaranga beach varies from 16.42% to 24.47%. The important minerals are ilmenite, rutile, zircon, sillimanite, garnet, monazite, pyroxene and others. For all samples a set of sieves bearing ASTM nos. 30, 40, 60, 80, 100, 120, 140, 170 and 200 corresponding to 0.59 mm, 0.42 mm, 0.25 mm, 0.177 mm, 0.149 mm, 0.125 mm, 0.105 mm, 0.088 mm and 0.074 mm respectively were used to separate different size fractions. The sieve mesh sizes vary from 0.59 mm to 0.74 mm. It was observed that maximum concentration of heavies was confined to +200 ASTM sieve or 0.74 mm. The total average heavy mineral concentration and light mineral concentration was found to be 20.07% and 79.49% respectively. The concentration percentage of different heavy minerals varied from higher to lower in the order like ilmenite, zircon, sillimanite, garnet, rutile, pyroxene, monazite and others. The ilmenite mineral in this area is found to have altered to secondary phases like pseudorutile, leucoxene and rutile along the fractures, cavities and grain boundaries. The alteration condition was observed as streaks, irregular patches, bands, and rim like structures around the ilmenite grains. Detailed study of alteration in ilmenite was carried out by Energy Dispersive Spectrometer (EDS) attached to Scanning Electron Microscope. The potentialities of heavies found at different locations of the Astaranga beach suggested a good source for the exploration. The alteration of the mineral ilmenite and high concentration of heavy minerals clearly pointed to the sedimentary environment and mechanical concentration process due to repeated wave action.
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In this paper preliminary mineralogical characterization of hematite from Alinci is presented. Several crystals of hematite were collected for research. The straight-forward identification of the studied mineral sam-ples was enabled by optical microscope, SEM-EDS, ICP-MS and XRPD methods. The use of these methods showed that they are very useful methods for rapid mineral analysis contributing important analytical information. With these methods was established that the investigated mineral is hematite. Hematite crystals occur in the syenites. The size of the crystals is up to 2 cm. Crystals of hematite included small idiomorphic to hypidiomorphic crystals of rutile and ilmenite. Idiomorphic to hypidiomorphic crystals of ilmenite are corroded, relictized and separated as a solid break-down solution in a homogeneous FeO–Fe2O hematite mass. Twinned idiomorphic aggregate of ilmenite partially cata-clased into a homogeneous Fe-oxide mass also appear. Relict and corroded hypidiomorphic to allotriomorphic forms of rutile appear in a compact and homogeneous Fe-oxide hematite mass. EDS analyses on samples from Alinci show that hematite matrix contains from 1.59 to 5.89 % of Ti, whereas the rutile domains may contain from 1.15 to 1.50% of Fe.
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The range of temperature within which tourmaline can arise in nature has not hitherto been determined. No synthesis of this mineral is on record, and experimental data are therefore lacking. On the other hand, rutile, brookite, and anatase have all been prepared synthetically, and the experimental data suggest their rutile is formed at the highest temperatures, brookite at temperatures considerably lower, and anatase at a point still lower on the scale. It is generally conceded that for rutile a pyrogenic origin is possible, and that brookite and anatase appear only as secondary minerals. The status of tourmaline as a possible pyrogenic mineral is regarded as doubtful by Clarke, who states that' in igneous rocks tourmaline seems to have been produced by fumarole action, and not as a direct separation from the magma'.
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Extensive negative aeromagnetic anomalies in the Modum area, south Norway, derive from rocks containing ilmenite with hematite exsolution, or hematite with ilmenite exsolution, carrying strong/stable reversed remanence. Here we describe a 2.5 cm thick high-temperature metamorphic vein of exsolved titanohematite. Reflected-light and EMP analyses show it contains three types of exsolution: spinel plates on (001); rutile blade satellites on spinel oriented at angles of ~60-90° to titanohematite (001); and lamellae 0.1-0.3 mm thick too fine for EMP analyses, also parallel to (001). Powder XRD gave a = 5.0393 Å, c = 13.7687 Å, V = 302.81 Å3 for titanohematite (≈Ilm9), and unrefined reflections of rutile and geikielite. Overlap EMP analyses showed enrichment in MgO, TiO2, and lack of Al2O3, indicating a mixture of titanohematite and geikielite. Non-overlap analyses showed the titanohematite is 6%Fe2+TiO3, 2%MgTiO3, 92% Fe2O3, generally confirmed by TEM-EDX analyses that also showed the geikielite is 30%Fe2+TiO3, 70%MgTiO3.
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조선누층군 최하부에 해당하는 면산층은 Ti-Fe 산화광물인 금홍석이나 티탄철석이 수반되어 발달한 퇴적층이다. 본 연구는 가곡면 풍곡리에 위치한 면산층을 중심으로 하부의 홍제사화강암 접촉부와 상부의 묘봉층을 대상으로 현미경관찰, X선 회절분석, 전자현미분석, 휴대용 X선 형광분석 및 대자율 측정을 통해 Ti-Fe 산화광물의 산상 및 구성비, 광물 및 지화학조성 변화를 해석하였다. 면산층은 주로 암회색 내지 회색을 띠며 사질부분과 이질부분이 교호하는 특징을 보인다. Ti-Fe 산화광물은 주로 석영입자와 더불어 산출되며, 독립된 결정을 이루는 금홍석은 흔히 외곽부에 티탄철석과 적철석이 발달하여 산출된다. 또한 적철석 내 티탄철석이 용리조직을 형성하기도 한다. 면산층을 하부, 중부 및 상부로 구분할 때 금홍석 및 적철석 함량은 하부에서 각각 평균 3.4%과 4.0%이며 상부로 가면서 평균 1.9%과 3.2%로 감소한다. 티탄철석은 하부에서 상대적으로 높고(평균 1.6%) 상부로 가면서 반복적인 변화양상을 보인다. 금홍석의 TiO₂ 함량은 면산층 하부에서 상부로 가면서 감소하며, 티탄철석의 TiO₂ 함량도 금홍석과 마찬가지로 하부(평균 53.09 wt.%)에서 상부(평균 50.41 wt.%)로 가면서 감소하는 경향을 나타낸다. 휴대용 X선 형광분석결과 홍제사화강암 접촉부에서의 Ti 함량은 최대 4.5wt.% 이르고, 면산층 상부는 2.2 wt.%, 그리고 묘봉층에서는 0.8 wt.%로 감소한다. 이러한 면산층 Ti-Fe 산화광물의 조직, 함량 그리고 Ti 조성변화는 하부에서 상부로 가면서 광물군과 티타늄 함량이 순차적으로 변화하는 고철질 화성암체로부터 기인되었음을 시사한다. The Myeonsan Formation represents the lowest strata of the Joseon Supergroup and comprises sedimentary rocks that contain various Ti-Fe oxide minerals such as rutile and ilmenite. Distributions of the Ti-oxide minerals and their petrography and geochemistry of the Myeonsan Formation are examined using microscope, X-ray diffraction, electron probe microanalysis, portable X-ray fluorescence analysis, and magnetic susceptibility. Our study focused on the Ti-bearing rocks in the Gagok area of the Myeonsan Formation, which are in contact with the Precambrian Hongjesa granite at the bottom and the Myobong Formation at the uppermost part. The Myeonsan Formation has dark gray or gray colors and shows alternating sandy- and muddy-rich layer. Ti-Fe oxide minerals commonly occur with quartz. Rutile mainly exists as an independent grain surrounded by ilmenite and hematite on the rim. Ilmenite commonly occurs with hematite by forming exsolution intergrowth. In the Myeonsan Formation, the contents of rutile and hematite are 3.4% and 4.0% at the lower part and decrease to 1.9% and 3.2%, respectively, toward the upper part. Ilmenite in the lower part has a relatively higher TiO₂ contents (approximately 1.6%) compared to the upper part, which exhibits repetitive variations. Similarly, rutile shows a decreasing trend of TiO₂ content from the lower to the upper part. In-situ analysis using portable X-ray fluorescence indicates that the Ti contents in the rocks reaches a maximum of around 4.5 wt.% near the contact between the Hongjesa granite, but decreases to approximately 2.2 wt.% in the upper part of the Myeonsan Formation and to about 0.8 wt.% in the Myobong Formation. The mineral texture and compositional distribution of the Myeonsan Formation suggest that the Ti-bearing minerals were derived from mafic igneous rocks, which exhibited a successive compositional variation from bottom to top.
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