CLASSIFICATION OF ORB DEPOSITS. 371 



arating bedded deposits of sedimentary origin from those which were formed 

 later than the inclosing rocks. Lottner also bases his classification on out- 

 ward form alone, but distinguishes secondary from original deposits. Von 

 Groddeck lays much more stress on genetic distinctions, and not only 

 brings in each of those recognized by the two previously named, but admits 

 the existence of ore deposits of later formation than the country rock which 

 do not necessarily fill pre-existing cavities or fissures. 



F. Posepny, 1 professor at Pfibram, who has made an extensive study 

 of ore deposits, including many of those of the United States, proposes an 

 even more radically genetic subdivision of metalliferous deposits into (1) 

 deposits in pre-existing cavities and (2) those formed by gradual replace- 

 ment of the rock substances by the vein material or mineral, the first class 

 being further subdivided into those filling cavities formed in a mechanical 

 way, or dislocation spaces, and those formed by corrosive action in soluble 

 rock, or corrosive spaces, which would correspond in general, though not 

 necessarily in all cases, to the distinctions of Grimm and Groddeck of the 

 fissure-fillings and cave-fillings. 



In order that a classification should find general acceptation among 

 mining men, it is essential, moreover, that it should be simple, concise, and 

 of easy comprehension, qualifications which the first two of the above 

 systems certainly do not possess. Thus, in this country, where mining 

 geology has found its principal discussion in courts of law, in which Prime's 

 translation of von Cotta has been generally accepted as authority, ore 

 deposits of primary origin (leaving placers out of consideration) are practi- 

 cally divided into true fissure veins and deposits which 'are not true fissure 

 veins, the latter class being somewhat loosely subdivided into contact 

 deposits, blanket deposits, and rake, pipe, and gash veins. 



The term "blanket deposit" is probably derived from the mania of the 

 Spanish miners, a term which in Mexico and South America designates the 

 richest and most productive ore bodies, but in the United States is apt to 

 be applied in rather a derogatory sense to any horizontal sheet of ore. The 

 last terms are derived from local usage in the lead regions of the north of 



1 Archiv fur praktische Geologic, p. 600. Wien, 1880. 



