Mineralogy. 129 
It will be observed that in several of the above formulas the two sili- 
cates of the formula differ widely in oxygen ratio; thus, in Ripidolite, 
the protoxyd silicate has the ratio 1: 1; while the peroxyd bas the ratio 
3: I=RSit, a very doubtful possibility under any circumstances. 
Viewing these same ratios in a different manner, that is, taking the 
ratio between the sum of the oxygen of the protoxyds and peroxyds 
and that of the silica, more simple results are obtained, and the paral- 
lelism with the Andalusite Section of Silicates is brought out. We thus 
make out four groups, as follows: 
1. General Formula (R*,#) Si-++ Aq. 
2. “ “ (R3, ¥) Sif tag. 
Gs is « (R*, #) Si® + Aq. 
ie «“ (R?, B) Si? + Aq. 
In Clintonite, whose ratio corresponds to sk, 5Al, 2Si, 3H, if 2A1 re- 
Place silica, the species has the general formula (Rs, 8) Si? + Ag, like 
Chloritoid (A). . 
Again, in Thuringite, if one third of the alumina replace silica, the 
formula may be (R, #) (Si, Xl) analogous to that of Hisingerite. 
Writing out the proportion of R# to ®, these formulas become : 
Group I. General Formula (R®,#) Si + Aq. 
Hisingerite (A), Fe? Sito¥eSitoH =(gFe* + 3¥e) Sits 
se oR s¥e? Si+ Fe Sitoml = (are? +3%e) 8i+ 2} 
Thutingite, fe Sit+RGLAN+3H = (he?+4H) Gi, +14 
Pyrosclerite (A),* 9h Si4- Al Si+ 6It = (3R* + 4A) Si+ 2 
Euphyllite, ReSi4skiSiter | —(gR*+ $A Si+ gH 
; Il. General Formula (R*, #) Sit + Aq. 
* haan (B, «= she Sit LORS + at = (Re + 2B) SF +149 
Chlonite  t ; 5? Sit + 3h Si#+ 19 = (eR? +28) Sit +142 
Delessite, fe Sit+HSit + oft — (gh? + 4H Sif + 14st 
IIL General Formula (R3, #) Sit+ Aq: 
Ripidolite, witzasttsn =@k? + ipsiP+iyt 
Aphrosiderite, Fe stpast+or =@re+iysit+H 
Clintonite, RG, ATL HEL Sy i — GR +) Gi Ani + it 
Chloritoid (4), “W!Sit+omst+ on =a@r?+eens#+H 
IV. General Formula (R?, #) Si?-+ Aq. 
Chloritoid (B) «= (ssa +eaiSiF+sH@ = GR’ + 221) Sit + anf 
Margarite, (ee) sit+emst =a, wy + east 
Cronstedite, RStpRSt+ st = = GR + se) Et +1 
Sideroschisolite, Fe? Sit 4 1300 pee Oe 
* The first of these formulas of Pyroscletite corresponds to Silica 376, aici . 
it, magnesia na 
2 mag 832, water 14-9; the second, (which accords i 
by H sa eies ake Ciccies Teersaupaul 326, am 130. Other analy- 
wT Gthese by Genth, and Smith and Brush, afford an intermedia ratio. 
Olinochlore has for R3:# nearly the ratio 7: 4, instead of 5 : 3. 
Secon» Senres, Vol. XVIII, No. 52—July, 1854. 
