b CONTENTS. 
Page. 
VIII. Influence of impurities _ _ _ . 31 
Miscellaneous impurities..-- ._.. __.. _. 31 
Hematite and magnetite _ . . 32 
Galena 32 
Nickel and cobalt 32 
Arsenopyrite . _ 32 
Chalcocite and bornite . _ . 33 
Chalcopyrite ......_ . . _ . 33 
IX. Form of occurrence of copper in copper- bearing pyrites .... 34 
Oxidation experiments _ 34 
Detection of chalcopyrite in pyrite or marcasite and in rocks. 35 
X. Miscellaneous specimens and specimens of doubtful nature. 35 
Table, and descriptions of specimens . . . 36 
Conclusions ... ... ...... r . 38 
Dr. Juliens specimens, table, and descriptions ... .... 39 
Discussion of Julien's hypothesis 39 
XI. Paramorphism ....... . . . . _ ... . 40 
XII. Constitution of pyrite and marcasite: action of cupric salts. .. . 41 
Experiments with cupric sulphate and pyrite. 42 
Experiments with cupric sulphate and marcasite 43 
Experiment with cupric chloride and pyrite ... . . . 41 
Experiment with ferrous and cupric sulphates 44 
Theory of thereaction 44 
General conclusions from the experiments . 45 
XIII. Oxidation of pyrite and marcasite by potassium permanganate 4(> 
XIV. Summary of results... __ . . .. 47 
Index ... 49 
