134 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



its natives as mineral tallow and the locality as Anderson's "taller bank." 

 Some workmen, while digging out the underlying iron ore for the blast furnace 

 at Shoals, laid bare, in the summer of 1874, the full thickness of the stratum 

 of kaolin and the attention of Mr. Cox was called to it. Tn his introduction 

 to the Sixth Report he devotes eleven pages to a description of the kaolin, 

 which he named "indianaite," and of its variety allophane, giving analyses 

 and his theory of their origin. The latter is of interest as coming from a chem- 

 ist of his repute. He says: "The clay lies immediately beneath the Mill- 

 stone grit or pebbly conglomerate of the coal measures and here occupies 

 the place of a bed of Archimedes limestone which is seen in situ about two 

 miles southeast of the mine. The overlying sandstone is very ferruginous 

 and the base, whei'e exposed to the weather, has decomposed and covered 

 the clay in places to a depth of eight or ten feet \vith ferruginous sand and 

 pebbles. There is a constant oozing of water from this sandstone which has, 

 no doubt, played an important part in the chemistrj- of the clay and hematite 

 deposit, for, though similar in its chemical composition to kaolin, this Law- 

 rence County clay differs physically and owes its origin to an entirely dis- 

 tinct set of causes and effects. While kaolin is derived from the decomposi- 

 tion of the feldspar of feldspathic rocks, such as granite, porphjTy, etc., the 

 porcelain clay of Lawrence County has resulted from the decomposition, by 

 chemical waters, of a bed of limestone and the mutual interchange of mole- 

 cules in the solution, brought about by chemical precipitation and affinity." 



In other words, he asserted that the La\vrenee County kaolin, which has 

 a clay base of 45% silica, 38% alumina and 16% combined water, is the result 

 of the chemical action of water percolating tlirough a sandstone upon the 

 beds of limestone. How such water can change the elements calcium and 

 carbon into silica and alumina passeth understanding. 



The most plausible explanation of the origin of the Indiana kaolin is that 

 set forth by Ashley,* which was based upon a theory of Lesquereux, \az., that 

 the kaolin occupies the horizon of Coal I, the coal and kaolin being never 

 found at the same place though often they occur but a short distance apart, 

 and that the kaolin was formed ])y the burning of a vein of coal immediately 

 abov(! a vein of underclaj', the impurities of the latter being consumed and the 

 kaolin left as a residue. 



This kaolin was used for a time for making porcelain ware but, being 

 wholly non-plastic, was not found suitable for the purpose and so Cox's 

 prophecy that: "The importance of the discovery of this clay can hardly 

 be overestimated, since it places within our reach the means of becoming 

 independent of Europe for fine grades of chinaware," was not fulfilled. It 

 was afterwards shipped for ten years to Philadelphia and used in the making 

 of alum cak(\ a product used in paper manufacturing. For the last 20 years 

 or more the deposits have not been worked. 



*23rfl Ann. Rep. Iiul. IJipt. (icol. 1.S9S, O.'U. 



