Vermiculite

About: Vermiculite is a research topic. Over the lifetime, 2320 publications have been published within this topic receiving 37142 citations.

Biotite - Hydrobiotite - Vermiculite in Soils

Abstract: IN the course of experiments dealing with the potassium chemistry of a group of alluvial and colluvial soils of California derived largely from weathering products of granite–diorite, we have observed the occurrence of minerals, presumably alteration products of biotite, which include trioctahedral vermiculite1 and hydrobiotite2,3 (regularly interstratified biotite–vermiculite). The minerals occur in some abundance in the fine sand, silt, and 0.5–2µ clay and are responsible for from 20–50 per cent of the cation-exchange capacity of the soils examined. A typical X-ray diffraction pattern for a magnesium–silt fraction, showing 25-A and 12.5-A peaks from hydrobiotite, 14.48 and 7.24 A diffraction maxima from vermiculite and a 10.1-A mica line is reproduced in Fig. 1A. Only 10.1-A and 7.1-A peaks were observed after saturation with potassium and air-drying, while sodium saturation resulted in peaks at 22.5, 12.3, 11.25, and 10.1 A. Treatment of magnesium material with glycerol or ethylene glycol did not change peak positions.

Effects of clay mineralogy and physico-chemical properties on potassium availability under soil aquic conditions

Abstract: Aquic conditions performed for paddy cultivation may cause many nutritional problems. Clay mineralogical composition plays an important role in this relation by affecting many physico-chemical and biological characteristics of soils. Three forms of K including unavailable, slowly available and readily available K, ex- ist in equilibrium in the soil system. Relationships between soil potassium forms with the clay mineralogical suite and physico-chemical properties were determined in 33 soil samples collected from five from paddy soils, two from kiwi fruit and one from citrus land pedons in the North of Iran. Mineralogical analyses showed that smectite, illite and vermiculite were the most abundant clay minerals in the studied soils. Mean soluble and exchangeable potassium in paddy soils were rather low compared to non-paddy soils due to potassium fertilization in non-paddy soils. Non-exchangeable potassium in the samples containing smectite as dominant clay mineral was lower than the samples dominated by vermiculite, hydroxy-interlayer vermiculite (HIV) and illite. Inability of the studied soils for potassium fixation was related to prevailed montmorillonitic type of smectite, which its layer charge origi- nates from octahedral sheet. Significant correlations (0.56 ** , 0.54 ** , 0.56 ** ) were ob- tained between exchangeable potassium and clay content, organic carbon and cation exchange capacity respectively. Therefore, taking into account both exchangeable and non-exchangeable K beside clay mineralogy and physico-chemical properties gives better indications for K potential and soil-quality management, compared to exchangeable form of K alone.

Native fixed ammonium and fixation of added ammonium in relation to clay mineralogy in some ontario soils

Abstract: Six soil profiles belonging to the Brookston, Lockport, Guelph, Chinguacousy and Haldimand series were sampled in southern Ontario. Illite contents of the clay fractions ranged from 25 to 56% and vermiculite contents ranged from 13 to 53%. The native fixed ammonium content varied from 57 to 367 μg/g and accounted for between 3 and 44% of the total nitrogen, being proportionally less in Ap horizons. Results of simple linear regression analyses demonstrated significant correlations of native fixed ammonium with percentages of clay, illite, illite plus vermiculite and K2O. The amount of ammonium fixed increased with increasing concentration of added ammonium up to the highest rate of application (2000μg NH4+/g soil). Regression analysis indicated that vermiculite was more important in the fixation of added NH4+ than illite. Studies on Ap horizons comparing the amount of NH4+ fixed with the amount of K− fixed for equivalent amounts of added cation showed that K+ was fixed in greater quantities than NH4+. Key ...

Granitic weathering: a Brazilian study

Abstract: Summary Chemical and mineral studies were carried out on weathered materials from six profiles developed on granites located in different areas of Brazil. Quartz and K-feldspar are the most abundant minerals overall. Kaolinite is the most common secondary mineral and is principally a feldspar weathering product. Mica breakdown is associated with smectite formation in semi-arid regions. In more humid regions mica weathering products include interlayered mica-vermiculite, vermiculite and kaolinite. Changes in the concentrations of Si, Al and K reflect the weathering behaviour of quartz, kaolinite, K-feldspar respectively, although K mobilities sometimes appear to be governed by processes related to the formation of secondary minerals. Ca and Mg are the first elements to exhibit depletion and their removal rates are very fast relative to K. P is also among the most mobile elements. Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba and Pb concentrations were measured. The first row transition metals are the most depleted. Rb and Sr are retained relative to Na, Mg, and Ca, and Ba accumulates as weathering proceeds. Y, Zr, Nb and Pb concentrations show little variation. The conclusion is that the factors controlling deep leaching are complex and the common notion that weathering rates are higher at lower latitudes should be reassessed.