Quartz illite

The nodules are found in gray-black commercial slate having fine grain size, uniform color and texture, and well developed slaty cleavage. Such slate occurs in thick strata marked only by thin black bands ( ribbons ) of somewhat coarser texture, and by rare, disseminated knots, siliceous nodules of foreign material. The slate is a mixture of quartz, illite, chlorite, caldte, and muscovite, with minor amounts of pyrite, carbonaceous matter, and heavy mineral grains. The dark color is attributed to finely disseminated carbon and pyrite. An analysis of the slate is given in Table I. 

This study has shown that the sample of Devonian shale is composed primarily of silicates with much lower amounts of carbonate minerals. Here, as with the Green River shale sample, the silicate minerals were associated primarily with the organic-rich areas of the shale, and when present, the carbonate minerals were found mainly in the organic-poor areas. The siliceous minerals of this Devonian shale sample were found to be quartz, illite, and muscovite, with trace amounts of kaolinite. Calcite, dolomite, Fe-rich dolomite or magnesite, and siderite were observed in the carbonate regions of the Devonian shale. However, the... 

Eastern U.S. oil shales are also sedimentary rocks. However, in contrast to Green River shales, the mineral constituents of Eastern U.S. shales are primarily silicates, with only about 1 wt% carbonate minerals. The bulk mineralogical composition of the Kentucky shale consisted primarily of quartz, illite and kaoli-nite, with some chlorite and pyrite. This is consistent with elemental analysis data which found the major mineral constituents to be Si, Al, Fe, and K. The elemental Ca concentration was less than 100 ppm. 

Based on analysis of authigenic smecite formed at 1°C (A(sm-H2O)=30.3 %o), natural smectite-illite pairs, the quartz-illite curve of Eslinger and Savin (1973), and the quartz-H20 curve of Matsuhisa et al. (1979). 

Borehole instability arises mainly in geochemi-cally sensitive smectitic (S) shales, usually of higher porosity (>10%), and in low-porosity (<10%), highly fractured, quartz-illite (Q/I) shale. These rocks are encountered in most deep drilling operations in both tectonic and non-tectonic situations. The origin of the fractured shales is of geological and practical interest. 

Magnetic resonance probing of specimens of 15-20% porosity smectitic shales (Pierre II shale from Wyoming, -40% smectite) indicated that -5% of the water content was fully free , not structured by electrostatic forces acting on the polar water molecules. Similar tests of a quartz-illite shale (Queenston Shale from Ontario) showed that -50% of the interstitial water was free , despite a much lower porosity (6-8%). Magnetic resonance relaxation curve analysis allows volumes of water at different binding energies to be quantified (Dolinsek et al., 1999). 

MacGillivray, D., Davidson, B. Dusseault, M.B. 1996. One-dimensional thermal conductivity measurements in quartz-illite and smectitic shales. Proc. Eurock 96, ISRM Int. Symp., Italy, Balkema, 107-113. 

Calcite Quartz Illite Chlorite Dolomite Feldspar... 

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