Differential Thermal Analysis of Clays and Shales, a Control and Prospecting Method*

Abstract

The differential thermal method, by determining the thermal reactions undergone by a clay or shale, is a rapid means of identifying the mineral components of such materials, and because the properties of clays and shales depend largely on their mineral composition, it is at the same time a rapid method of evaluathg the properties of such materials.Differential thermal analyses are presented for the pure forms and synthetic mixtures of the common components of clays and shales, namely, kaolinite. halloysite, illite, montmorillonite, quartz, gibbsite, boehmite, diaspore. dolomite, d a t e , gypsum, organic material, pyrite, marcasite, goethite, and limonite.Differential thermal analyses are presented also for a variety of well-known types of clays, and on the basis of the thermal data for the pure components, the mineral composition is indicated. The correlation of mineral composition of clays and shales (as re5ected in the differential thermal curves) with the ceramic properties is discussed as a basis for using this thermal method to indicate the properties of such materials.Finally, differential thermal analyses are presented for sequences of samples from the pits of several operating clay products plants in order to illustrate the way in which the method can be applied in prospecting and in plant control.

Thermal, ceramic and technological properties of clays used in production of roofing tiles - principal component analysis

“…The third degradation stage, associated to decarboxylation of calcite, is manifested with an especially intense endothermic reaction in corresponding DTA/DSC curves for MP9 and MP10, moderately for MP7, MP8, and barely visible in the cases of LE14 and LE17. The endothermic minimum in the DTA curve of MP9 sample, ascribed to decarboxylation of calcite, was at a higher temperature compared to the other samples probably due to the presence of dolomite [16,17]. Very wide and small endothermic peak from 600-900 o C in DTA curves for VL3-4 and LE16 accompanied with a negligible mass loss, supporting previous findings, is related to the absence of carbonates.…”

Bentonite deposits of the northern Black Hills district, Wyoming, Montana, and South Dakota

“…A few small pyrite crystals were observed in grit washed from the undiscolored clay; in the thermal diagram ( fig. 90F) of an undiscolored sample, pyrite is recognizable by a characteristic double exothermic inflection corresponding to a reaction between 4000 and 5000C, similar to that described by Grim and Rowland (1944). The pyrite does not occur as finely divided particles, however, as is indicated by the absence of this reaction in a -2-mu fraction of the same undiscolored sample ( fig.…”

“…The apparatus used for the differential thermal analyses was similar to that described by Grim and Rowland (1944). The samples were first placed in an atmosphere with a relative humidity of 46 percent and left there for several days.…”

Synthesis and characterization of bentonites rich in beidellite with incorporated Al or Al–Fe oxide pillars

“…In the range from 400 to 550°C, endothermic peak related to the dehydroxylation of interlayer pillars and octahedron layers in smectite occurred. It is common for beidellite to udergo dehydroxylation at these temperatures [39]. The temperature of dehydroxylation of the PILCs shifted to lower values in comparison to that of the Na-B2.…”