i8 73 .] 



Mineralogy. 



265 



MINERALOGY. 



Considerable interest was excited a short time back by M. Jeremejew's an- 

 nouncement that he had discovered diamonds imbedded in a rare Russian 

 mineral known as Xanthophyllite.* Wishing to verify Jeremejew's observa- 

 tions, Dr. Knop, of Carlsruhe, has been quietly working at the subject, and 

 has recently come to the conclusion that the so-called crystals of diamond 

 are merely angular cavities, suggesting, it is true, the well-known forms in 

 which the diamond is wont to crystallise, but nevertheless destitute of the 

 veriest trace of diamond, or of any other mineral substance. It might, how- 

 ever, be fairly supposed that the cavities, though now empty, originally con- 

 tained certain crystalline materials which impressed their angular form upon 

 these hollows. Some curious experiments by Knop lead, however, to an 

 opposite conclusion. He obtained thin sections of xanthophyllite, which, 

 when magnified 1500 diameters, appeared to be absolutely destitute of any of 

 these angular cavities : nevertheless, after treating the preparation with sul- 

 phuric acid, numerous cavities were recognised exactly similar to those referred 

 in other cases to the presence of diamonds. In other experiments, fine 

 lamellae of xanthophyllite were carefully examined in all directions under the 

 microscope, and the entire absence of any crystalline impressions thus deter- 

 mined ; the object was then touched with a few drops of concentrated sulphuric 

 acid, and heated until white fumes appeared. The preparation, when cooled, 

 was protected with a cover-glass, and placed under the microscope, when it 

 exhibited swarms of beautiful tetrahedral cavities, sharply defined, regularly 

 formed, and arranged in parallel rows. From these and other observations, 

 the author feels justified in concluding that the angular cavities in the Russian 

 xanthophyllite have nothing to do with the presence of diamonds, but owe 

 their origin merely to the corrosive action of acids. 



Further " Mineralogical Notices," by Prof. Maskelyne and Dr. Flight, have 

 been published in the " Journal of the Chemical Society." The first portion 

 of the present communication refers to the heterogeneous substances grouped 

 together under the name of Isopyre. It appears that these are, for the most 

 part, merely impure forms of opal, associated with other mineral substances. 

 The rare species to which Brooke, many years ago, gave the name of Percylite, 

 — an oxychloride of lead and copper, occurring in beautiful blue crystals, 

 belonging to the cubic system, — has hitherto been known only by a single 

 specimen, said to have come from Sonora, in Mexico, and now exhibited in the 

 British Museum. It is, therefore, of interest to learn from Prof. Maskelyne 

 that Percylite has been found among minerals from South Africa. Among 

 other points of interest in this paper, a comparison is suggested between cer- 

 tain minerals from Redruth, in Cornwall, and those recently discovered at 

 Schneeberg, in Saxony, and attention is called to the simultaneous presence 

 of bismuth and uranium in association with arsenic, in minerals from these 

 widely-distant localities. 



Another recent contribution to British mineralogy is due to Prof. Church, 

 who has communicated to the Chemical Society some analyses of certain 

 mineral arseniates and phosphates. The minerals examined comprise some 

 transparent crystals of the fluor-apatite known as asparagus stone (Werner's 

 Spargelstein) ; the rare species arseniosiderite, which occurs in a deposit of 

 manganese-ore at Romaneche, Macon; and the West of England minerals — 

 CJiildrenite, ehlite, tyrolite, and wavellitc. 



Breithaupt, the venerable mineralogist, though retired from the professorship 

 which he so long held in the Mining Academy of Freiberg, in Saxony, has not 

 rested from his labours. Unable, through loss of sight, either to read or to 

 write, he dictates to his assistant, Herr Frenzel, and has thus been able to 

 contribute to Leonhard and Geinitz's " Jahrbuch " some recent " Mineralo- 

 gical Notices." Among these notices he gives the full characters of the 

 mineral which he described some time ago as Nantokite. This is a chloride of 



* See Quart. Journ. Science, No. XXXII., Oct., i87i,p. 541. 



