386 Scientific Intelligence. 



In a Report by Mr Swainson, an enumeration is given of 213 (?) species 

 of Casuarina, commonly called He and She Oaks, but which, according 

 to Mr Swainson, are the true pines of Australia. 



MINERALOGY. 



Mineralogy of the Dolomite of the Alps. By Sartorius von 

 Walterhausen. 

 The author's investigations relate chiefly to the dolomite of the Bin- 

 nenthal, which is remarkable from its containing in the middle of the 

 deposit several small parallel veins containing a number of foreign mine- 

 rals belonging to the classes of sulphurets, oxides, carbonates, silicates, 

 and sulphates. Each of these groups have been separately examined. 



Sulphurets. — These consist of zinc-blende in fine twin crystals, iron 

 pyrites, small scales of orpiment, and beautiful transparent crystals of 

 realgar. Besides these there is a gray sulphuret which consists of seve- 

 ral minerals. This gray sulphuret was first described and analyzed under 

 the name of Dufrenoysite by Damour, who ascribed to it the formula 

 2Pb S-f-As S 3 . It is described as crystallizing in the regular system, al- 

 though its formula is identical with that of Federerz (glumosite) as ana- 

 lyzed by Rose, which contains antimony in place of arsenic, and whose 

 form is prismatic. The conclusion to be drawn is, either that there exist di- 

 morphous forms belonging to this composition, or that Damour's descrip- 

 tion refers to two substances, one examined chemically only, the other 

 crystallographically. The author considers the latter to be true, having 

 found by extended examination on the spot that several minerals exist 

 which differ both in composition and form, but which are easily con- 

 founded in the massive state. For the mineral crystallizing in the regular 

 system the name of Dufrenoysite is retained. The crystals generally 

 have the form of the garnet dodecahedron or icositetrahedron. They 

 occur isolated in the dolomite , and seldom reach the size of a pea. Their 

 colour is dark steel-gray passing into iron- black. Their analysis gave 

 these results, to which we have added those obtained by Damour for his 

 mineral : — 



Damour. 



Sulphur, 27*546 22-393 



Arsenic, 30-059 20'778 



Silver, 1*229 0*190 



Lead, 2-749 25-999 



Copper, 37-746 0-260 



Iron, 0-824 0*380 



100-153 100-000 

 From which there can be no doubt the two substances are different. Von 

 Walterhausen' s result corresponds with the formule R 2 S -\- ASS 2 -f- RS, 

 and belongs to an entirely new group of minerals, being the first example 

 of a sulphuret in which arsenic exists in the form of realgar. It is clear 

 that Damour's analysis does not apply to the true Dufrenoysite crystal- 

 lizing in the regular system ; and, as an additional proof, the author has 

 carefully determined the specific gravity of the regular crystals, and 

 found it to be 4-477, while Damour found that of his mineral to be 

 5-549. On the examination of a large number of specimens from the 

 Binnenthal lead, gray crystals belonging to the right prismatic system 

 were found accompanying Dufrenoysite, which were so extraordinarily 

 brittle that they could not be separated entire from the matrix. The 

 ratio of the axes is a : b : c = 1 : 0*96948 : 0-63335, and several modifi- 

 cations were observed. Their specific gravity was 5*393, and analysis 

 afforded the following result : — 



