18G9.] Mineralogy. 307 



been subjected to cbemical examination by Herr Kammelsberg.* 

 From the behaviour of the mineral when exposed to heat, he infers 

 that the molecule of water which it contains is present in a state 

 of true chemical combination, and not simply as water of crystal- 

 lization. The formula of dioptase thus becomes 



H2 Cu Si O^ 



and the mineral is therefore isomorphous with the two corresponding 

 hexagonal silicates, "Willemite and Phenakite, the former containing 

 Zuj Si O4, and the latter Be. Si O4. 



Some time ago we had occasion to notice the discovery of a 

 native hydrous arseniate of zinc from Chile, described under the 

 name of Adamite.] This species has lately been obtained by Messrs. 

 Gory and Boutigny from a small copper mine worked in the Keuper 

 sandstone of Cape Garonne in the Dept. du Var. The French 

 adamite occurs in the form of lenticular crystals or thin plates on 

 the walls of fissures traversing a quartzose rock, and is associated 

 with the two arseniates, olivenite and cobalt bloom ; the latter 

 imjjarts a reddish tint to many of the crystals, which otherwise 

 present a greyish colour. | 



In compliment to Professor Laxmann, the Siberian traveller, 

 the name of Laxmamiite is proposed by M. A. E. Nordenskjold for 

 a new mineral discovered at Beresow, in Siberia. § It appears to 

 be a chromate and phosphate of lead and copper ; its chemical 

 composition being represented by the following formula, where 

 KO=PbO + CuO: 



3 (I EO, i HO) PO5 + 2 (3 EO, 2 Cr O3). 



The component minerals of some of our Cornish granites have 

 lately been examined by the Rev. Dr. IIaughton.|| He finds that 

 these rocks contain two felspars and two micas ; the felspars, he 

 refers to the species orthoclase and albite, and the micas to lepidolite 

 and lepidomelane. Dr. Haughton supposes that these constituents 

 are common to aU the granites of Cornwall and Devon, which thus 

 bear a close resemblance in mineralogical composition to the granites 

 of Leinster and Mourne. 



Analyses of two titaniferous magnetites from Norway have been 

 published by Mr. David Forbes ; H and a large number of chrome 

 iron-ores have been chemically examined by M. J. Clouet, whose 

 memoir on these minerals is supplemented by a note in which 



* Zeitschrift d. deutsch. geolog. Gesellsch. Bd. xx., p. 536. 



t ' Quart. Journ. Science,' vol. iii., p. 427. 



+ 'Comptes Eendus/ Dec. 7, 1868, p. 1124. ' Geol. Mag.,' Feb., 1869, p. 79. 



§ ' Journal fiir praktische Chemie.' Band cv., No. 22, p. 335. 



II 'Proc. Eoyal Society,' vol. xvii.. No. 108, p. 209. 



•H ' Chemical News,' Dec. 11, 1868, p. 275. 



