1824.] Scientific Notices — Mineralogy. 389 



It is greatly to be wished that this extensive genus were sub- 

 jected to a more systematic examination than it has hitherto 

 received, and as has already been done so successfully in the 

 case of the pyroxenes and amphiboles. The accuracy of the 

 preceding formula is indeed supported by strong arguments ; 

 but many, particularly of the older analyses, are contradictory 

 of it, and the simplicity of the crystalline form of garnet renders 

 peculiarly necessary a severe induction of facts, before it can be 

 regarded as demonstrated that there are not at present con- 

 founded under this name several genera of minerals, which are 

 essentially distinct from one another, even on the broad basis of 

 the isomorphous theory. 



8. On Meionite. 



Our mineralogical readers are aware that within these few 

 years analyses of this mineral have been successively published 

 by Arfwedson, Gmelin, and Stromeyer. The results of the last 

 two chemists were almost identical ; but those of Arfwedson 

 disagreed with both so materially, that it was obvious that either 

 he or they must have been engaged with a different mineral from 

 meionite. M. Arfwedson, inalettertoSchweigger, acknowledges 

 his mistake, and states, that on repeating the analysis with an 

 authentic specimen, he had obtained results which indicated 

 exactly the same formula with those of Gmelin and Stromeyer. 

 It is singular that the mineral which he originally analyzed, 

 although scarcely differing in composition from leucite, was 

 easily fusible before the blowpipe; whereas leucite is quite 

 infusible.— (J ah rbuch der Chemie und Physik, vs.. 347.) 



9. Erlanite, a new Mineral. 



Lustre, feebly shining to dull. Streak shining, with a fatty 

 lustre. Colour, light greenish grey : streak, white. Massive. 

 Sometimes compact, sometimes in small and fine granular dis- 

 tinct concretions. Fracture in some specimens foliated, in 

 others splintery and even. Its structure is distinctly crystalline, 

 but no specimen has yet been observed which admitted of regu- 

 lar cleavages. Hardness, between that of apatite and actyno- 

 lite. Sp.gr. from 3-0 to 3-1. Before the blowpipe, it melts 

 easily into a slightly coloured, transparent, compact pearl, and 

 resembles gehlenite more closely than any other known mineral : 

 from felspar it is distinguished by its greater sp. gr. ; from 

 Saussurite, by its inferior sp. gr. and hardness. 



It was discovered in 1818 by Briethaupt in different parts of 

 the Saxon Erzgebirge. It forms a part of the oldest gneiss 

 formation, and is always mixed with more or less mica. Between 

 Gros-Pohle and Erla there exists a bed of it at least 100 fathoms 

 in thickness. It has been used for upwards of 200 years as a 



