1895.] Mineralogy. 361 | 
which agree perfectly with those of Cedarstrém and Rimbach. Traube 
has contributed to the same paper the almost identical results of an 
analysis of the same material, so that there can be little doubt that 
2Fe,O, 3TiO, is the correct formula of the mineral. Frenzel points 
out the absurdity of the supposed isomorphous relation with andalu- 
site. Neglecting the earlier analyses by Koch and by Lattermann on 
imperfectly purified material, the analyses that have been nade of 
pseudobrookite are as follows: 
I Il opal IV V VI 
TiO, 44.26 42.49 33.59 42.89 42.35 42.896 
Fe,O, 56.42 58.20 66.42 56.37 57.65 57.104 
Total 100.68 100.69 100.01 99.26 100.00 100.000 
I. Cedarstrém, II. Rimbach, III. Doss, IV. Frenzel, V. Traube, VI. 
theory from formula 2Fe,O, 3TiO, 
Formula of Staurolite.—Rammelsberg® takes exception to the 
formula for staurolite recently proposed by Penfield’ (HAI,Fe Si,O,,). 
He claims that the analyses of staurolite show the mineral to repre- 
sent chemically three varieties, as follows ey A, where R: R, = 1:2; 
Ir I 
B, where R: R, =1:2.5; and C, where R: R,=1: 3. Penfield’s for- 
mula, he states, is nota general one because it only represents the analy- 
ses which fall in group B. 
® Neues Jahrb. f. Mineral., etc. Beil. Bd., ix, pp. 480-484, 1894. 
ï Am. Jour. Sci., (3) xlvii, pp. 81-89, 1894. 
Wm. H. Hosss. 
