Clay Minerals

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Clay Minerals


a group of hydrous silicates comprising the majority of clays and determining their physicochemical, mechanical, and other properties. Clay minerals are predominantly the product of weathering of aluminosilicates and silicates of magmatic and metamorphic rocks at the surface. In the process of weathering the clay minerals undergo sequential transformations of their structure and chemical composition, depending on the changes in the physicochemical conditions in the weathering and sedimentation medium. The particle size of clay minerals in clays rarely exceeds 0.01 mm. According to their crystalline structure, clay minerals belong to the schistous or pseudoschistous silicates. The crystal lattices of typical clay minerals consist of alternating networks of silicon-oxygen tetrahedrons (silicon ions in tetracoordinate configuration) and of hydroxyl octahedrons surrounding atoms of aluminum, iron, or magnesium. In this case, divalent magnesium is present in every octahedron (trioctahedral silicates), whereas trivalent aluminum is present in two out of three octahedrons (dioctahedral silicates).

Clay minerals with two-level structures consist of tetrahedral and octahedral networks, such as the kaolinite group—for example, kaolinite, dickite, nacrite, and halloysite. Clay minerals with three-level structures consist of two outer tetrahedral networks and an inner octahedral network. Members of this category are the hydromica group, for example, hydromuscovite and glauconite (potassium atoms are located in the spaces between layers); the montmorillonite group, for example, Al-montmorillonite and Fe-montmorillonite, or nontronite (water and exchange cations are located in the spaces between layers); and the chlorite group, with alternating three-level layers and spaces between the layers (octahedral networks) in the structure. Clay minerals of more complex structures are also known.

Definite differences in the chemical composition of the clay minerals correspond to the crystallochemical differences in their structure. As a result of this property, the clay minerals differ sharply from one another. Thus, for example, montmorillonitic minerals have very high exchange capacities and adsorption properties, but these properties are weakly developed in kaolinitic materials. The clay minerals belonging to the hydromica group increase greatly in volume upon heating. Structural determinations on clay minerals are performed by infrared spectroscopy and by chemical, X-ray, electron-diffraction, electron-microscope, and thermal methods.


Ginzburg, I. I., and I. A. Rukavishnikova. Mineraly drevnei kory vyvetrivaniia Urala. Moscow, 1951.
Rentgenovskie metody izucheniia i struktura glinistykh mineralov. Moscow, 1965. (Translated from English.)


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The findings reveals that soft tissue fossils are generally found in rocks rich in the mineral berthierine, one of the main clay minerals identified by the previous study as being toxic to decay bacteria.
The quantitative distribution of clay minerals in the pelitic fraction was determined by the simulation of 1-dimensional XRD patterns of disordered layered minerals using PyXRD software (BSD-2 Clause 2016).
Further, soil K dynamics based on type and age of clay minerals play an important role in crop nutrition of potassium.
The inorganic constituents described [6] are: (i) calcite of foraminifera shells and fine-grained matrix, (ii) authigenic quartz filling the chambers of some foraminifera, composing tests of siliceous algae (supposed), and very limited detrital quartz, (iii) phosphate in pellets, intraclasts, bone, teeth, and coprolites of carbonate fluorapatite, clay minerals thought to be detrital in origin, (iv) pyrite as filling the chambers of shells and voids.
Acid treatment of clay minerals, namely fibrous clays, smectites [14] and Kaolinite [15], is widely applied in order to optimize their physicochemical behaviour, aiming better industrial properties.
Weaver [15] summarized the detrital origin of clay minerals in sedimentary rocks and they strongly reflect their source material and only slighty modified in their depositional environment.
Through downhole observations, SEM and X-ray diffraction analysis, we can see fillings in coal fractures as that most of the clay minerals are kaolinite or illite, and the carbonate fillings in both macro-scale fracture and miro-scale fracture are also abundant.
Buhmann C, Fey MV, de Villiers JM (1985) Aspects of the X-ray identification of swelling clay minerals in soils and sediments.
XRD analyses showed similar mineral associations in both gravel and sandy levels, that mainly consist of dolomite, calcite, quartz, clay minerals and feldspars (Table 1).
Marathon Valley became a high-priority destination for the Opportunity mission when mineral-mapping observations by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), aboard NASA's Mars Reconnaissance Orbiter, located clay minerals (a type of phyllosilicate) in this valley.
The technology utilizes geopolymerization of clay minerals, which can be sourced from quarry and mine waste, plus construction site excavation.