1873-] Mineralogy. 537 



stack of the ovens to the production of steam. No water is introduced into 

 the ovens, as is done in the old system, but the coke is watered after it has 

 been withdrawn, and thus absorbs about 3 per cent of water. 



MINERALOGY. 



A mournful interest clings to a memoir in a recent number of " Poggen- 

 dorff 's Annalen," descriptive of Gustav Rose's researches on the action of 

 heat on diamond and graphite. This memoir represents, indeed, some of the 

 last work in the long and active life of the great mineralogist of Berlin — a life 

 which extends over nearly seventy-five years, and was brought to a close on 

 the 15th of last July. Although it is beyond our purpose to trace the history 

 of Rose's scientific labours, we may yet point to the long list of papers in the 

 Royal Society's Catalogue — a list numbering upwards of 120 memoirs — in 

 proof of his extraordinary activity, his devotion to original research, and the 

 success with which he cultivated mineralogical science, whether in its geome- 

 trical, its chemical, or its geological aspect. 



Rose's last paper, which was communicated a few months ago to the Berlin 

 Academy, is the outcome of some lengthened researches on the behaviour of 

 diamonds at high temperatures. To some extent these observations confirm 

 those of Schrotter and others who have worked in this direction. For 

 example, Rose found that by placing crystals of diamond between carbon- 

 points in vacuo, and subjecting them to the action of a Siemens's dynamo- 

 electric apparatus, the diamond became red-hot, and eventually flew to pieces, 

 and at the same time the surface acquired a black crust which had all the 

 characters of graphite. Exposed to the temperature at which cast-iron melts, 

 the diamond was found to undergo no change, but at the fusing-point of 

 wrought-iron it became quite black and opaque, exhibiting a strong metallic 

 lustre, and becoming, in fact, converted into a graphitic substance. But the 

 most curious point in the behaviour of diamond rs seen when the gem is 

 heated in a muffle, with access of air. Under these circumstances the faces 

 of the diamond exhibit regular triangular depressions, reminding one of the 

 markings common on many of the South African diamonds. Some interesting 

 examples of these symmetrically developed etchings are figured in the plates 

 accompanying the memoir in " Poggendorffs Annalen." 



As so much discussion has been rife with respect to the nature of the 

 colouring-matter of the emerald, — one party referring it to an oxide of chro- 

 mium and another to an organic source, — it is interesting to find that the 

 subject has lately been taken up by Mr. C. Greville Williams, F.R.S., who has 

 communicated his researches to the Royal Society. On exposing a South- 

 American emerald to a bright reddish-yellow heat for three hours, in a platinum 

 crucible, the green colour was not destroyed ; hence the author was led to 

 disconnect the question of colour from that of the presence of carbon. Indeed 

 a colourless Irish beryl was found to contain rather more carbon than a richly- 

 tinted emerald. The author believes that there is no room for doubting the 

 correctness of Vauquelin's conclusion, that the green colour of the emerald is 

 due to the presence of chromic oxide. Experiments on the fusion of beryl 

 and emeralds showed that these gems lose density when fused, but this fact 

 cannot be used in argument against the formation of such minerals at a low 

 temperature ; for it is quite possible that they were crystallised from a fused 

 mass which was originally formed at a temperature sufficiently high to keep 

 the constituents of the emerald in a state of fusion, and that the crystals 

 developed during a slow process of cooling. 



Von Kobell has lately described, under the name of Kjcrulfin, — a name 

 suggested in honour of the Norwegian mineralogist and geologist, Kjerulf, — a 

 new mineral-species from Bamle, in Norway. The substance had been deter- 

 mined by Rode, of Porsgrund, to be a new phosphate of magnesia, and com- 

 plete analyses by Von Kobell and Wittstein lead to the following formula : — 

 2(3MgO.P 2 5 ) + CaF 2 . Kjerulfin is therefore very similar in composition to 

 the rare mineral known as Wagnerite. 



