382 Review of Dana’s Mineralogy. 
** Primary form, an oblique rhombic or rhomboidal prism; M: T= 
110° to 98°, crystals having the faees M smooth and ihe give the 
latter, which therefore appears to be the correct 
angle of the prism. Seeondary form, the annexe 
figure; P : M=105°, P : €=1338° 30’, M : e=120° 
30’, P : a=132°,(D.) The terminal planes dull 
allel to the longer diagonal, and producing brilliant 
surfaces ; parallel to M indistinct. Crystals usually 
long and slender. Occurs also long fibrous, paral- 
fet or slightly a 
3°2—3'238, D.; 3°259, Norton. (Yorktown.) 
ete vitreous, inka to pearly ; hardly shining on M, but splendent 
on the face of perfect cleavage ; parallel to P, vitreous, inclining to re- 
sinous. Streak white. Color hair-brown—grayish-brown. ‘Translu- 
cent. Fracture uneven, parallel to P. Brittle. Tite long crystals are 
detached from the rock entire, with great difficulty, on account of their 
frangibility. 
“Composition, according to Bowen, (Sill. Jour. yi, 118,) Muir, 
(Thom. Min. I, 424,) Connell, (Jameson’s Jour. xxx1, 282,) and Nor- 
ton, performed for this work, in the laboratory of B, Silliman, Jr. 
Chester, Conn,* Chester. Chester. Yorktown, N. ¥. 
Silica, 42-666 38-670 36°75 37.700 
Alumina, 54111 _ 35°106 58°94 62°750 
Zirconia, 18-510 
Oxyd of iron, 1-999 7-216 0:99 2287 
Water, 0.510 
99:286,B. 99°502,M. 96°68, C. 102:739,N. 
“*'The analyses by Connell and Norton show that this mineral con- 
tains no Zirconia. 
“Before the blowpipe, both per se and with borax it is infusible. 
“Obs. The crystal here figured appears to have dissimilar lustre on 
M and T, and this, as well as the secondary planes, indicates that the 
primary is probably a rhomboidal prism. In composition, Sillimanite is 
very close to Kyanite, if they are not identical ; yet its bright and bg 
cleavage shows that it is mineralogically distingt from that species.” 
(pp. 377, 378,) 
Connell proposed (Jameson’s Jour., Vol. xxx1, p. 232) the union 
of Sillimanite with Kyanite, and Berzeliust in his report for this 
hin eS phigh BA LKw 
* Chester, Ct. is quoted in Thomson and other a authors as Saybrook, Ct 
t Arsbert® Kemi och Min. (Swedish edition,) 1843, p 
aie 
ay 
