. * | 
é Scheerer on Isomorphism. 65 
which admits of being thus written (R)? Si+(R): Fe. This 
formula differs from that of chlorite from the member (R) Si 
jab contained therein but singly, whereas in chlorite it is 4 
c doubled, and that it contains peroxyd of iron instead of alu- 
mina. ‘That cronstedtite finds a place among the minerals of the 
chlorite family by the new formula here proposed for it, is with- 
out doubt amply borne out by its external characters. Its nagap 9 
line form is a hexagonal prism, with a cleavage — el 
terminal plane. 
Chlorite, npidalies peppune and the other chlorite minerals 
treated of here, all receive, as is seen above, formule consisting of 
two iii a which, generally speaking, are very simple. 
One of these members consists of a silicate, the other of an 
inate or an oxydate of iron. 
C. silicates of magnesia and alumina, and bases ethno 
therewith. 
ef _ (a.) Mica and micaceous minerals. 
1. Mica from Iviken. (Svanberg. ) 
36°97 3: 774: oars (R) S32 1B Sis, 
36:97 : 7°40 : 2-47. 
2. Mica from Bratistad. (The same.) ~ 
33-08 : 12-66 ; 1:93 ae ens 
32-00 : 12-80 : 213 : (R) Si+2R Sit, 
-'The analysis gave an excess of 0-89. 
3. Mica from Broddbs. (The same.) 
24-92 : 16°95 ; 2:39 
be 25-00 : 16°66 : 2-77 : (R) Si+2R Si. ‘ 
Very closely agreeing with the mica from Utén, Kimito, Fahlun <> 
Ochotsk, according to the analyses of Henry Rose. If a , 
sail quantity of manganese which is given in Svanberg’s anal- 
ysis as oxyd is calculated as protoxyd, the formula agrees evell 
closer, inasmuch as in that’ case the oxygen ratio is then = | 
2499 16-61 : 2-73. oa 
Wee 4. Mica from Rosendal. (The same. ) 
23°07; 3°%87 ; 10-45 * 
93.61: 787 : 1049 3¢ QR) Sil Si. 
F 5. Mica from Pargas. (The same. ) 
| SRA Bim eS a eS 
i 23:00 13:20 + 6605 eet ee ; 
©The analysis gave 1-19 Joss 
re 6. Mica from Monroe, (v. Kobell.) 
278 11-06 
Wee 10803 : 10-50 : (Ry S148 Si, 
Szcoxp Serizs, Vol. VI, No. 16.—July, 1848. 9 
