. Bulletin of the Geological Society of America. Geology. 486 T. C. HOl'KINSâCAMBROSILURIAN ORES tlie argillaceous and silicious matter in the Beam, and not in direct con- tact with the limestone, which is a sandy, silicious variety. Leaving on the weathered surface, in places, a silicious skeleton or framework some- times coated with ore. The ore is laminated parallel with the walls of the seams. As the limestone decays, the thin sheets of ore break down and mingle with the residual clay, furnishing the commercial ores. The ore which occurs in place in the seams in the limestone and
. Bulletin of the Geological Society of America. Geology. 486 T. C. HOl'KINSâCAMBROSILURIAN ORES tlie argillaceous and silicious matter in the Beam, and not in direct con- tact with the limestone, which is a sandy, silicious variety. Leaving on the weathered surface, in places, a silicious skeleton or framework some- times coated with ore. The ore is laminated parallel with the walls of the seams. As the limestone decays, the thin sheets of ore break down and mingle with the residual clay, furnishing the commercial ores. The ore which occurs in place in the seams in the limestone and the frag- ments visible in the residual clay are all thin and fragile so far as ob- served ; but the bottoms of the ore pockets are concealed by debris, and it is possible that the sheets become thicker at greater depths, as is frequently reported by the workmen. In the slate areas the ore with the other residua rests upon a mass of clay, in many cases white clay, stained locally by iron oxides. As the slates from which the clays are derived are interstratified with the lime- stones, there can be no very sharp distinction drawn between the ore deposits on the limestone and those on the clay. In many districts the greater part of the ore deposits are found on the white clay. So common is this occur- rence that it may be stated Figure 3.âIdeal Section Illustrating Possible Modt of Accum- <\S a general rule that ill ulatinq Iron Ore underneath tin Clay by Process of Seqreaation -, ,1 t and Leaching. areaS where the cla~VS 0CCUr they are associated with the ore deposits, but where the clays are absent the ores occur in the eroded cavities in the limestone, as described above. One general distinction can be made between the purely limestone deposits and the limestone- clay deposits. The latter are generally richer at the bottom in direct contact with the white clay, while the former may be as rich at the top as at the bottom. Solid bodies of ore are spoken of by the miners in m
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