Scientific Intelligence — ^iineralorjij and (Jlunudry. 185 



99.77 

 Hence the formula is 4 Mg S + Aq, and the Villarsite is to be re- 

 garded as a monosilicate of magnesia. Except that it contains watei-, 

 this newly discovered substance has the same composition .as cryso- 

 lite ; but, v/hile the proportion of water is too large to admit of its 

 presence being regarded as accidental, the external, crystallographic, 

 and chemical characters are opposed to its being united with that 

 species. The Villarsite furnishes a new example of a mineial as- 

 sociated with Plutonic crystalline products containing water of crys- 

 tallisation. M. Dufrenoy remarks, that we are already in possession 

 of analyses which prove the presence of water in rocks evidently vol- 

 canic, and hence concludes, that it is not necessary to have recourse to 

 the theory of infiltrations for the explanation of the occurrence of 

 zeolites in basalts, trachytes, and even in traps. 



23. Xenolite. — This new mineral is so named Irom its not belong- 

 ing to the locality where it is found. It occurs along with Wbrth- 

 ite, near Peterhoff, in boulders, which are probably derived from Fin- 

 land. It is crystallized in prisms, united together in very delicate 

 fibrous masses. On being separated, the fibres are found to be 

 three-sided prisms, in which two of the sides form an angle of 45^ 

 38', and the third seems to be at right angles to one of the others. 

 Tliere is a terminal plane. Hardness = that of quartz. Sp.gr. = 

 3.58. It is colourless, but occasionally presents greyish or yellowish 

 portions. Translucent. Fracture uneven, granular. Lustre vitreous, 

 and, on the more distinct cleavages, pearly. Gives no water before the 

 blowpipe. Infusible in fragments and in powder. Fusible with diffi- 

 culty, along with borax and phosphate of soda. According to an analy- 

 sis by M. Komonen, this mineral consists of silica 47.44, and alumina 

 (with a little oxide of iron) 52.54 = 99.98. {Poggendorff's Annal. 

 1842, No. 8, from paper by Nordenskiold in the Act. Soc. Scic?it. 

 Fen?iica', vol. i. p. 372.) 



24. Sulphuric and Molyhdic Acids. — Dr Thomas Anderson of 

 Lcith has lately made some experiments on the relations of these 

 two acids. The molybdic acid dissolves in the sulphuric, but the 

 combination cannot be made to crystallize by evaporation. ] low- 

 over, on decomposing iiiulybdatc of baryta with an excess of sulphuric 



