Geology and Mineralogy . 89 



occurred the most extensive differentiation affording the comple- 

 mentary alkalic felsic and mafic types. Every petrographer will 

 find these discussions of the pedogenesis and classification of the 

 rocks of great interest, based as they are upon such accurate data 

 and presented so clearly. l. v. p. 



6. Brief Notices of some recently described Minerals. — 

 Baethite is a zinc-copper arsenate, described by W. Henglein 

 and W. Meigen, from Guchab in the Otavi mountains, German 

 South West Africa. It occurs as a crystalline incrustation on 

 quartz crystals which form druses in a reddish dolomite. Hard- 

 ness 3; specific gravity 4-19; color grass-green; luster greasy. 

 An analysis gave : 



As 2 O s P 2 O s ZnO CuO H 2 insol. 



64-0 1-0 23-3 8-5 3-2 1-1 = 101-1 



For this the formula SZnO.CuO.SAs^O^H^O is calculated. — 

 Centralbl. Min., 353, 1914. 



Ussingite is a new silicate, described by O. B. Boggild, from 

 the remarkable locality at Klangerdluarsuk, Greenland. It is 

 referred to the triclinic system on the basis of cleavage frag- 

 ments. Hardness 6 to 7; specific gravity 2-50; luster vitreous to 

 pearly; color violet-red. An analysis by Chr. Christensen gave: 



SiO„ A1 2 3 Na 2 H 2 



58-74 17-73 19-91 4-19 = 100-57 



This leads to the formula HNa 3 Al (SiO a ) 3 .— Zs. Kryst., liv, 120, 

 1914. 



Faratsihite isahydratedferric silicate described by A. Lacroix, 

 from Faratsiho, Madagascar. It occurs in masses of a yellow 

 color, resembling nontronite. Under the microscope it shows a 

 crystalline structure like that of kaolinite, being made up of aggre- 

 gates of minute hexagonal scales. An analysis gave: 



SiO„ A1 2 3 Fe 2 3 H 2 O(105°) H 2 0(red heat) X 



41-60 22-68 15-22 5-71 13-02 1-44 = 10020 



Here X = FeO 0-54, MgOO-11, CaO 0-60, Na 2 0-16, K 2 0-22, 

 TiO, 0-13, P 5 B 0-21. The formula deduced is H 4 (A1, Fe), Si ? 9 , 

 and it may be regarded as a kaolinite in which part of aluminium 

 is replaced by ferric iron. — Bull. Soc. Fr. 3Iin., xxxvii, 231. 



Speziaite is a kind of amphibole described by L. Colomba, from 

 the pyroxenite of Riondello, Traversella. It occurs in fibrous and 

 acicular forms with cleavage angle of 55° 30' to 56°; color green, 

 pleochroic; the angle C/\C = +23° to 24°. An analysis gave: 



SiO, Al 2 O s Fe 2 3 FeO MnO CaO MgO Na 2 K 2 H 2 



36-21 0-79 34-57 3"56 0'67 10-53 7"87 4-08 0-93 0'50 = 99-71 



The calculated formula is that of an orthosilicate 5Fe 4 (Si0 4 ) 3 .12 

 (Ca, Mg, Fe, Na 2 , HJ Si0 4 . — Atti Accad. Sci., Torino, xlix, 

 March, 1914. 



Lublinite is described by R. Lang as a monoclinic modification 

 of calcium carbonate forming the soft earthy aggregate called 



