Gabbroid Rocks of Minnesota. — Wine Iw 11. 235 
Vogelsand LaVirador QS^SO ' Ab^An, 
Obermayer 
A. N. Winchell 
A. N. Winchell 
A.N. Winchell 
Vom Rath 
Fouque 
Ab^An, 
A. N. Winchell^ Carlton Peak 94'-''16' Ab-^An, 
Scharizer Jan Mayen 94" AbgAn. 
Vom Rath 
Vom Rath 
LaVirador 
93''50 ' 
Kiew 
93^52 ' 
Labrador 
93^54 ' 
Kiew 
OS^SG ' 
Kamenoi Hrod 
93°58 ' 
Tannenbergsthal 
91" 9- 
Pico 
9i"21 ' 
Average 
93^59' 
Carlton Peak 
94'-''16 ' 
Jan Mayen 
94'' 
Hufnofiord 
95"15 ' 
Hafnotiord 
95°25 ' 
Lveragef 
Ol'^SS ' 
Mull, Hebrides 
93°38 ' 
Holland Mull. Hebrides 9.3°38 ' Ab.An^ 
These results may be represented graphically in connection 
Avith the valties ordinarily accepted for the other feldspars, as 
follows: 
1. Albite pg'^ (ooi)A(oio) =93° 36', determined by Marignac and 
Des Cloizeaux on material from St. Gotthard, and generally accepted, 
though Tschermak seems inclined to prefer a smaller angle, as low 
as 93° 10' (see Tschermak: Min. 1894. p. 472, but cf. p. 466). 
2. Oligoclase, pg'^{ooi)A{oio) 93° 28', determined by vom Rath 
on feldspar from Vesuvius of composition nearly AbiAui, but analysis 
somewhat discordant; this is accepted by all the best mineralogies of 
the present time, though they also accept Tschermak's theory with 
which it is clearly discordant, 
3. Andesine, ^^^ (ooi)A(oio) =^93° 46', determined by vom Rath 
on crystals from Sardinia containing 60.2% SiOa and showing certain 
optic properties characteristic of andesine. Universally accepted. 
4. Labradorite, pg'^ {001) K{oio) = 93° 32'; average of nine de- 
terminations which have been made hitherto on material which was 
probably of the composition AbiAu;. (See above.) 
5. Labradorite, /^,^' (ooi)A(oio) = 93° 52', accepted as correct 
by Obermayer after four measurements resulting: 93° 40', 93° 44', 93^ 
48', and 93" 50', on material unanalyzed, but probably near AbyAus; 
accepted by most authorities at present. 
6. Labradorite, pg'^ {001) i\{oio) = 93° 59', average of seven de- 
terminations which have been made on material of the composition 
Ab7Ans, nearly. (See above.) 
*One might add to this: A. N. Winchell, Poulkoiika /^^'•'(ooi)A(oio) 
=94'^ 12'. 
tWithout the value of Scharizer the average would be 95''20 ' 
