_ J. D. Dana’s Mineralogical Contributions. 219 
3, Monometric. Garnet, ($2343) Si Helvin, (2R344Be) Sit 
Pyrope, (i83+28)Si in which R=Mn, Fe, Mn S, 
4. Dimetrie. Zircon, Br Si Meionite, (3023-541) Si 
Idocrase, ($R3-+48) Si Seapolite, (2R3-+42Al) Si 
« (283428) Si Mellilite, (¢R3-+4#) Si 
Sareolite, (4R3-+4Al) Si 
5. Monoclinic. Epidote, (483-4333) $i | Zoisite, (3-124) Si 
(283428) Si Gadolinite, 82 Si 
Allanite, (4R2+38) Si 
6 Triclinic. Danburite, ({0a3-+28)5i Axinite, (83, 8, B) Si 
V. Ratio 1: 3(to 3-4). Includes—Tviclinie, Kyanite, Sil- 
limanite; Monoclinic, Euclase and Sphene; Trimetric, Anda- 
lusite, Topaz, Staurotide, and perhaps Lievrite; Dimetric, Geh- 
lenite; Hexavonal, Tourmaliue. 
From the Formulas of Datholite, Tourmaline, Axinite, Dan- 
burite; it follows that these are not borosi/icates, the boracic acid 
being a buse. It is a general fact that all mineral species con- 
taining boracic acid are either hemihedral or oblique in erys- 
tallization. 
The Feldspars and some other species do not appear at first to 
come into this system, unless the alumina and silica are consid- 
red as replacing one another, and on this ground, any ratio be- 
tween 1:1 and 1:3 may be made ont. ‘he constaucy of the 
Oxygen ratio of R to # (=1:3) in the feldspars, seems to pre- 
clude our taking such a liberty with the Aland Si. ‘The follow- 
ing are the species, their oxygen ratios, old formulas, and the 
formulas proposed. 
: Oxygen ratio. Old formula. Formulas. 
1. Monoclinic.  Orthoclase, 1:3:13 kK Si+Al Sis (K+) Sit 
2. Trictinie, Albite, 1:3:12 Na Si+-A1Si3 (Na+) Si 
Oligoclase, 1:3: 9 RSitAISi2 (B+!) Sit 
Andesine, 1:3: 8 re Sie+sai sie (Rai) Sis 
Labradorite, 1:3: 6 R Si+A1 Si (R+-A) Bia 
Anorthite, 1:3: 4 Rs 'Si+3Al Si (R+A1) Sis 
The following species also belong to the section, as they have 
the same ratio 1:3 for the protoxyds and peroxyds; Leucite has 
the composition of andesite ; and sodalite, etc., that of anorthite. 
- \,* The formula of Helvin, as written by G. Rose, is (Min, Fe)* Sit+Be Si+MnS 
MnO. “But we conform as closely to the analyses, if we add 30-74MnS, ‘wh 
At becomes as above written, or (3 (48+4Mns)?+4Be) Si = Silica 345, glucina 
egg of manganese (part Fe in the analysis) 398, sulphuret of manga- 
‘Rese 16-3, 
je 
