MINERALOGY. 539 



and the crystallographical work of Groth. The species thomsenolite 

 and pachnolite, which, have often been confounded, are shown to be 

 distinct both in form and in composition. Cathrein has examined the 

 minerals called leucoxene and titanomorphite, both of which are altera- 

 tion minerals of titanic iron or of rutile, and has shown that they are 

 really identical with the common mineral titanite. It will be remem- 

 bered that Lasaulx attempted to set up titanomorphite as an independent 

 species on the ground that it was simply a new calcium titanate, but 

 the analysis of Bettendorff, on which the conclusion was based, is shown 

 to have been inaccurate. 



The gaseous inclusions in smoky quartz, especially that of Branch- 

 ville, have been studied microscopically by the late Dr. Hawes, and 

 chemically by Prof. A. W. Wright. W. E. Hidden has also described 

 large fluid cavities in the quartz of North Carolina. The Branchville 

 quartz is shown to be exceptionally rich in cavities with liquid carbon 

 dioxide, so much so that a thin fragment broken off by a tap of a hammer 

 separates with explosive force, and a fragment held in the flame of a 

 Bunsen burner flies to pieces with great violence. The analj^sis of these 

 gases by Wright has proved the presence, besides the carbon dioxide, 

 of nitrogen, sulphureted hydrogen, ammonia, sulphur dioxide, and fluo- 

 rine. 



Bamberger has shown that the picranalcite of Bechi, supposed to be 

 a distinct mineral, is ordinary analcite, containing only a trace of mag- 

 nesia. H. Sjogren has proved the presence of both chondrodite (mono- 

 clinic) and humite (orthorhombic) in Sweden, and he has attempted 

 to establish the chemical composition of these two closely related spe- 

 cies, as also of the third species of the group, called clinohumite. It 

 will be remembered that these are equivalents of Scacchi's three types 

 of Vesuvian humite: type I = humite, type 11= chondrodite, and type 

 III = clinohumite. 



The chemical composition of the zinc silicate, calamine, has been 

 established by Fook. He shows that it remains unchanged at 340 ^ 

 C, and loses its water only at a red heat; the water consequently 

 is not to be regarded as water of crystallization, but the true formula is 

 H2 Zn2 Si O5, it being thus a basic silicate with an oxygen ratio of 3 : 2 like 

 andalusite. A similar change had already been made earlier in the 

 method of viewing the composition of the copper silicate dioptase. 



Dr. Genth has published some new observations bearing upon the 

 subject of the alteration of corundum, a subject to which he devoted an 

 extended and important memoir in 1873. Some of the cases noted by 

 him are: (1) Corundum altered to spinel. At the Carter mine, Madison 

 County, North Carolina, corundum is found in white and pink crystals 

 and in irregular grayish- white or white cleavage masses enveloping a 

 variety of a delicate pink color ; this corundum is often more or less 

 completely changed to a massive greenish black spinel of a fine granular 

 structure, but rarely showing octahedral crystals in the compact mass. 



