* - r 



J 



3 

 5 



\ 



388 Mineralogical Notices. 



F 



In another trial, Si 33-17, and C<feS 16'50. Supposing the lime 

 combined with the carbonic acid^ it will leave [1], 16-36, [2], 

 16-13 of water. This affords the Berzelian formula^ 



corresponding to silica 33-29, alumina 13*31, peroxyd of iron 

 1-92, magnesia 35'50, water 16-00=: 100-02. In the Gerhardtian 

 notation, the formula according to Mr. Hunt is Si 0=^ (Al B\ Mg 

 H|), the oxygen ratio for the silica and bases being 17'515 : 34'990. 

 It approaches chlorite closely in composition, although not at all 

 foliaceous. The species is named in honor of Mr. Logan, who is 

 at the head of the Geological Commission of Canada. 



Matlockite^ a new Oxychlorid of Lead; by R. P. Greg, Jr., 

 (Phil. Mag., [4], ii, 120, August, 1851.) — Matlockite occurs at 

 the old mine of Cromford near Matlock, with corneous lead (phos- 

 genite, Haid.) Form dimetric ; occurs in tables which are gen- 

 erally thin and superimposed on each other, occasionally slightly 

 curved. Cleavage basal, but not perfect. A single crystal in the 

 hands of Mr. W. G. Lettsom is an inch square, an eighth of an 

 inch thick and transparent. The edges and angles are replaced ; i 



P:e = llP 50'; Pra-llO^ 34'; e:e = 97^ 58^ and 136^ 19S- 

 a : a = l04Q 6' a'nd 120^ 52^ Color yellowish, sometimes a little 

 greenish. Lustre adamantine and occasionally pearly. G.=7'2L 

 H. =^2-5-3, Composition according to Dr. R. A. Smith: 



Chlorid of lead 55-177, oxyd of lead 44-300, moisture 0-073 



99-549, giving the proportions of 1 of chlorid of lead to 1 of 

 oxyd of lead-chlorid of lead 55-46, oxyd of lead 44-53-^ 99-99. 



The corneous lead of the same locality afforded Dr. Smith, 

 Chlorid of lead 51-784, carbonate of lead 48-215-99-999, ^ 



Pyroxene and Hornblende. — Rammelsberg observes in his 4th 

 supplement, p. 106, that certain augites, as a black augite of Ta- 

 burg, analyzed by H. Rose, a brown from Pargas, by Nordens- 

 kiold, a black from the basaltic tufa of the Azores, by Hochstet- # 



ter, have the composition of hornblende ; while some hornblendes, 

 as a tremolite from Pennsylvania has the composition of pyr- 

 oxene. The species have been long known to belong to the 

 same system of crystallization, and to be mataally derivable, 

 and in uralite, as shown by G. Rose, there is an example of a 

 substance with the external form of augite and the cleavage 

 structure of hornblende. 



In volume Ixxxiii of Poggendorff's Annalen, p. 458, (July, 

 1S51,) Rammelsberg gives the results of analyses of an augite 

 and a hornblende from the basaltic tufa of Hartlingen in Wes- 

 tervvald. He obtained 



Si Xl te Mn Ca Sl^ 



1. Augite, 47-52 8-13 1302 40 18-25 12-76=10008 

 Oxygen, 2i6^ 3*79 2*89 0*09 5-19 5- 10 



2. Hornblende, 42-52 UOO 16-59 12-25 13 45 Na 1-71 K 1-92 lllOl^lOO*^ 

 Oi-ygen, 22-09 5- 14 268 3-48 538 043 032 



cr 



