Silicate minerals

About: Silicate minerals is a research topic. Over the lifetime, 1794 publications have been published within this topic receiving 67064 citations.

Reactions catalysed by minerals iv. the mechanism of the benzidine blue reaction on silicate minerals

Abstract: The oxidation of benzidine to benzidine-blue on silicate minerals is shown to occur at aluminium atoms exposed at crystal edges and at transition metal atoms in the higher valency state present in the silicate lattices. The transition metals in the silicate lattice undergo chemical oxidation-reduction reactions. Changes in the colour of the benzidine-blue radical cation with the conditions of reaction are discussed in terms of the solvent used for the reaction and its influence on the pH of the mineral surface.

Dissolved Products of Artificially Pulverized Silicate Minerals and Rocks: Part II

Abstract: Ten grams of previously analyzed, rock-forming silicate minerals (mica, 2.5 g) were ground under 100 ml of double-distilled, and CO2-charged, waters for one hour, and the centrifuged-clear solutions analyzed for dissolved constituents. The pH's of the slurries prepared in distilled water were 8 to 9, and in CO2-charged water, 5.5 to 6.9. Total amount of dissolved ions was higher in CO2-charged water than in distilled water. Grinding in distilled water was exposed to room temperature. Highest amounts in ppm of dissolved ions in distilled and CO2-charged waters, respectively, were from minerals as follows: Si, diopside, 23.3, and enstatite, 17.4; Al, nepheline, 2.2, and microcline 1.0; Fe, biotite, 14.3, none detectible in CO2-charged water; Ca, augite, 4.5, and hornblende, 13; Mg, enstatite and olivine, 12, and olivine, 150; K, microcline, 38.8 (K dissolved from 2.5 grams of biotite in distilled water was 35.4), and microcline, 69.3; Na, nepheline, 85.9, and nepheline, 114. Olivine dissolved nearly stoichiometrically (Mg and silica); aluminous and other Mg-rich silicate minerals show relatively reduced solubility of Si, some of which apparently combines with Al and/or Mg to form clay minerals. Dissolution of Mg is singularly much higher in CO2-charged water than in distilled water. No dissolved Fe was detected in CO2-charged water, demonstrating that residual concentration of iron oxide occurs by leaching of Fe silicates by carbonic acid. Elements extraneous to mineral formulas are enriched in the solution relative to others. Minor, or trace elements, such as Mn, Ga, V, Ti, Mo, Co, Sn, Pb, Zn, are dissolved in concentrations determined spectrographically in parts per billion.

Identifying source and evaluation of hydrogeochemical processes in the hard rock aquifer system: geostatistical analysis and geochemical modeling techniques

Abstract: In order to quantify spatio-temporal changes in the hydrogeochemistry of Swarnamukhi river basin, Andhra Pradesh, India, a total of 239 groundwater samples have been collected for pre- and post-monsoon seasons of 2014 and 2015. The geology of the study area is comprised of granite, granitic gneisses, shales, quartzites, laterites and recent alluvium along the river course. Based on the study of geochemical processes of different seasons, it is found that the occurrence of Na and HCO3 in 2014 shifted toward Ca and HCO3 in 2015 due to cation exchange process. Fe shows the higher concentration value than safe limit due to dissolution of ferruginous minerals and domestic sewage discharges. Bivariate plots of various ions and ratios depict the predominance of silicate weathering over carbonate and evaporite dissolution apart from anthropogenic activities in the enrichment of groundwater constituents. High nitrate concentration was observed in the urbanized regions of the basin followed by intense agricultural areas. Geochemical modeling was carried out using mineral saturation index and thermodynamic stability plots to deduce major weathered products. Most of the groundwater samples in the study area are saturated with carbonate minerals but are undersaturated with silicate minerals. Thermodynamic stability plots suggest the formation of kaolinite secondary mineral and presence of aluminosilicate minerals. Fuzzy calculation is applied to determine the water quality index, which categorizes a majority of the samples as excellent to good category for human use. Factor analysis points toward the mixed source identification of ionic constituents. Saline water mixing index model calculation suggests the effect of salinization in coastal areas due to heavy withdrawal of the fresh groundwater resources for various uses, whereas in the mainland it is due to agricultural runoff and domestic waste water.