338 The American Xutum/id. 



,A,,nl 



of MnSi0 3) M-Sio : ,„.l Mn S1,0,. A large number of chlorite 



analyses are communicated by Ludwig, 1 to wbom material was fur- 

 nished by Teshermak. Among the varieties whose composition was 

 determined are pennine, from the Zillerthal, cronstedtite, from Pri- 

 bram, korundophilite, from Chester, Mass., metachlorite, from Elbin- 

 gerode, daphnite, from Penzance, tabergite, from Taberg, prochlorite, 

 from the Zillerthal and the Fischerthal, leuchtenbergite, from Amity, 

 N. Y., and clinocldor, from Achmatowsk, Russia, and from Kariet, 

 Greenland. The figures for korundophilite and leuchtenbergite fol- 



SiO a Al-A FeA FeO MgO H a O Sp. Gr. 



Korund 23.84 25.22 2.81 17.06 19.83 11.90 2.87 



Leucht 30.28 22.13 1.08 34.45 12.61 2.68 



These analyses of Ludwig and others that have recently been reported 

 have afforded Tschermak 2 data for the elaboration of a theory con- 

 cerning the constitution of the chlorites, according to which the mem- 

 bers of this group of minerals are regarded as consisting of mixtures 

 of six molecules, four being represented by the known minerals ser- 

 pentine, amesite, strigorite and chloritoid, and the other two being 

 hypothetical Dr. Clarke' takes exception to Tschermak's views and 

 shows that upon his own theory (that the chlorites are substitution 

 derivatives of normal salts) the composition of these complicated 

 minerals becomes simple, and that his theory is as closely in accord 

 with the facts known as to the structure of the chlorites, as is the 

 theory of the Vienna mineralogist. In a discussion as to the rela- 

 tions of the recently discovered minerals pinakiolite and trimerite to 

 well known groups Brogger 4 places the former among the rhombic 

 aluminates, and the latter, as a pseudo-hexagonal species, between the 

 olivine and the willemite, groups. He further points out the simi- 

 larity in morphological properties between all of these groups and 

 ascribes their differences to morphotropic action. He regards all the 

 silicates of the general formula R 4 Si0 4 as composing a morphotropic 

 group, in which trimerite is triclinic because R is replaced by two 

 elements, viz: Be and Mn— Several micas, vermiculites, and - h ' ' '^' 

 have been investigated by Messrs. Clarke and Schneider 6 by the 



