198 Scientific Intelligence — Mineralogy. 



lustre adamantine ; colour orange yellow ; streak between orange - 

 yellow and yellowish-brown ; transparent to translucent ; easily 

 frangible, and somewhat brittle ; hardness = 2j to 3|- ; specilic 

 gravity, 5"158 to 5"191. The following are the component 

 parts (as determined by the analyses of Professor Plattner) of the 

 brown xanthokone formerly found, and the yellow xanthokone now 

 discovered : — ■ 



Brown Xanthokone. Yellow Xanthokone. 

 Silver, . . 64-181 . . 63-880 

 Sulphur, . . 21-35S , . 21.798 

 Arsenic, . . 13-491 . . 14-322 

 Iron, . . 0-970 . . 0-0 



100- 100- 



It thus appears that, notwithstanding the great similarity of the 

 yellow xanthokone to Greenockite in external appearance, the com- 

 position of the two minerals is widely different. — (jPo'jge^idorff' s 

 Annals, vol. Ixiv., p. 272 and 275.) 



28. Occurrence of tJie Silicates of Yttria and the Protoxide of 

 Cerium in the Saxon Erzfjehirge. — While occupied with an inves- 

 tigation of the felspars of the Erzgebirge, Carl Kersti-n analysed 

 the substance termed oligoclase by Breithaupt, from Bodeu, near 

 Marienberg, chiefly on account of its great resemblance to the 

 natron-spodumene from the granite near Stockholm. In some 

 fragments of this kind of felspar there were small blackisli-brown 

 disseminated portions, in which preliminary experiments indicated 

 the presence of a considerable quantity of the protoxide of cerium. 

 Subsequently, Kersten obtained a larger quantity of the dissemi- 

 nated mineral; and, upon a more minute examination, he ascertain- 

 ed that the blackish-brown portions are composed of two distinct 

 substances, of which the one approaches most nearly the Allanite of 

 the Jotun-Fjeld, and the second the orthite of Ytterby. As, how- 

 ever, the Allanite and orthite appear, from the investigations of 

 Scheerer, to be nearly allied, perhaps the two minerals from the 

 Erzgebirge may prove to be varieties of one species ; but this can 

 only be detei mined by quantitative analyses. — (Leonhard and 

 Bronn's Jahrhuch, 1845, Heft 2, p. 202, from Poggendor/'s An- 

 nalen, vol. Ixiii., p. 135.) 



29. Yttro-Titanite, a New Mineral Species described hy 

 Scheerer of Christiania. — In a quarry about seven English miles to 

 the north-east of Arendal, in Norway, at the southern extremity of the 

 island of Bu (Buoc), a considerable quantity of felspar occurs in the 

 gneiss, partly in tlie form of veins, and partly in irregular masses. 

 Close to the junction with the gneiss, Scheerer found in the felspar 

 the half of a round imbedded fragment, of the size of a fist, of a mi- 

 neral having the following characters : — One distinct cleavage, and 

 feeble traces of two others; fracture small conchoidal, passing into un- 

 even ; colour brownish-black ; the streak light greyish-brown ; trans- 



