70 



GEOIvOGY OF IvA SALLE COUNTY. 



Hematite. 180; red oxide of iron; oxyg-en, 30; 

 iron, 70; color dark, steel g'ray or iron black, with 

 metallic lusture; when scratched or powdered, cherry 

 red. Occurs as an ing-redient of some red clays. 



Limonite, 206; yellow or brown oxide of iron; 

 oxyg-en, 25.68; iron, 59.92; water, 14.4; lusture, slig-htly 

 metallic to earthy; color, from nearly black to brown- 

 ish yellow and ocher yellow. Found in yellow clays; 

 it also constitutes bog" iron ore. 



Quartz, 231; flint, chert, silica, sand, etc.; when 

 pure, oxyg^en, 53.33; silicon, 46.67; massive or crystal- 

 line; of almost all colors and shades; hard; will 

 scratch gflass; in lusture, from dull to g-littering-; very 

 common, as chert or flint in Trenton limestone; as sand, 

 a part of it crystals, in St. Peters sandstone, as cherty, 

 chalcedony, in concretions, in calciferous at Utica, and 

 as quartzite in the same formation at the Pequamsaug-- 

 g-in Cement Works. 



Clays.— Kaolinite, 419; Kaolin, porcelain clay, 

 silica, 46.3, alumina, 39.8; water, 13.9; has been 

 reported as occurring* in the county, but we have no 

 evidence to support the statement, and must say that 

 we doubt its accuracy. Saponite, 417, occurs in clays 

 over coal No. 2 and several other forms. 



Our clays may be regrarded as impure kaolins, but 

 they are not, as far as we have observed, crystalline in 

 structure. We shall, therefore, class them as brick 

 clays, usually from the drift; fire clays, usually from 

 below the coal beds; pottery clays, usually from below 

 coal No. 2. 



Many other minerals are found in the drift. It 

 would be possible to collect specimens, of half the 

 minerals known to man from this formation, but none of 

 them w^ere formed here, and none of them exist in such 

 quantity as to make them objects of interest farther 

 than to know what they are and where they probably 

 came from. 



