1869.] 



of the Breitenbach Meteorite. 



371 



which I applied some years since the term siderolites), was found in Brei- 

 tenbach in Bohemia. 



It is a spongy metallic mass, very similar to the siderolite of Rittersgriin 

 in Saxony, the hollows in the iron being filled by a mixture of crystalline 

 minerals. These minerals are two in number ; and the present notice 

 deals with these two minerals. 



1 . One of them is of a pale-green colour, crystallizing in the prismatic 

 system, and presenting at once the formula of an augitic mineral and a 

 crystalline form nearly approximating to that of olivine. Dr. Viktor von 

 Lang, when my colleague at the British Museum, measured some mero- 

 hedral crystals of this mineral, and obtained for its elements 



a:b:c=0'8757 : 0-8496:1, 



110.010 = 44 8 



10 1.100 = 41 11 



1 04.1 00 = 74 3 



11.010 = 40 16 



The analysis of this green mineral gave, from 0*4127 grm., — 



per cent. Oxygen-ratios. Equivalent ratios. 



Silica 0-2315 56-101 29*920 1-87 



Magnesia 1247 30*215 12*087 1*51 \ ,. 88 



Ferrous oxide .... 0-0560 13*583 3*018 0-37 J 



0*4122 99*899 

 results which correspond very nearly with an Enstatite of the formula 



(Mg 4 FepSi0 3 . 



The specific gravity is 3*23. 



It is remarkable that of the minerals presenting the general formula 



M Si0 3 , 



where M stands for one or more metals of the calcium and magnesium 

 groups, we are acquainted with two anorthic types (Rhodonite and Ba- 

 bingtonite); three oblique types, those, namely, of Wollastonite, of Horn- 

 blende, and of Augite ; two prismatic types, those, namely, of Enstatite 

 and Anthophyllite, homoeomorphous with the oblique Augites and Horn- 

 blendes ; and to these we shall have now to add (if the measurements of 

 Dr. Lang shall prove to be distinct from those of Enstatite) a third, in the 

 green mineral under description. 



Of these, the prismatic types are essentially those of the magnesian 

 group. The rest, with the exception of the calcium silicate (Wollastonite), 

 are types belonging to the mixed groups. 



2. The other mineral is one of very great interest. It is, in short, 

 silica crystallized in forms and in a system distinct from quartz, and pos- 



