The geology of Hardin County, and the adjoining part of Pope County . B. Reduced scale of figure A, showing its relation to larger mass of sphaleriteand to fluorite veinlet. Magnification 40 diameters. Illinois State Geological Survey Bulletin No. 41, Plate II-G. A. The principal feature of this figure is replacement of calcite (Ca) byquartz (Q) along twinning directions of the former. Galena (G) and sphalerite(S) also appear replacing calcite in the common manner—the galena with partialidiomorphic outlines in places, the sphalerite in irregular masses extending shortdistances along calcite tw
The geology of Hardin County, and the adjoining part of Pope County . B. Reduced scale of figure A, showing its relation to larger mass of sphaleriteand to fluorite veinlet. Magnification 40 diameters. Illinois State Geological Survey Bulletin No. 41, Plate II-G. A. The principal feature of this figure is replacement of calcite (Ca) byquartz (Q) along twinning directions of the former. Galena (G) and sphalerite(S) also appear replacing calcite in the common manner—the galena with partialidiomorphic outlines in places, the sphalerite in irregular masses extending shortdistances along calcite twinning striations. In this figure quartz includes bothsulphides. Fluorite (F) here replaces calcite. In adjacent areas—just out of this field—fluorite is to be seen plainly replaced by the sulphides. Magnification 50 diameters. Calcite Fluorite Chalcopyrite Pyrite Sphalerite Galena Quartz B. Shows the very generalized time relationships between the minerals, asworked out from a study of thin sections and polished surfaces. The abscissaemeasure paragenetic time, and the vertical dimensions of the individual mineralplots indicate relative amounts, not computed, of the respective minerals. —18 G ECONOMIC GEOLOGY 275 ORIGIN OF THE DEPOSITSVIEWS OF PRE
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectgeology, bookyear1920
