812 THE AMERICAN NATURALIST. [Vou. XXXII. 
This passes by addition of quartz into a rock called by the author a 
quartz-hypersthene-diorite, and by addition of brown hornblende 
into a type called a hornblende-gabbro, The norite consists of basic 
plagioclases, hypersthene, diallage, brown and green hornblende, 
biotite, a few accessory minerals, and decomposition products of 
the plagioclase. The diallage and hypersthene are often in parallel 
intergrowths. In the quartz-hypersthene-diorite biotite is more com- 
mon than it is in the norite. Brown hornblende is absent. In the 
hornblende-gabbro brown hornblende is more abundant than the 
pyroxenes. It is the characteristic constituent. Its prismatic angle 
is 124° 18' and its density 3.217—3.222. The mineral is pleochroic 
with a=yellow; b=reddish brown; c=yellowish brown. The 
extinction ¢/\¢ varies between 14° 30! and 15° 30’, A portion 
separated from the rock powder yielded when analyzed : 
SiO, AlO, FeO; FeO MnO MgO CaO Na,O K,O H,O. Total 
39-58 14.91 4.01 10,67 tr. 14.06; rJ 2.87 62 2.79 = 100.27 
This gives in calculation very nearly the formula (HKNa), 
(MgFeCa), (AlFe); SisO,¢, or in its generalized form R', R", R's 
(SiO4), a formula unusual for amphibole. The author suggests that 
there may be a group of amphiboles that are orthosilicates, though 
the greater number of them are unquestionable metasilicates. The 
three rock types described grade into each other by almost imper- 
ceptible changes, the gabbro and the diorite being peripheral forms 
of the norite. Analyses of the three rocks follow: 
SiO, TiO, AlO, Fe,0; FeO MnO MgO CaO NaO K,O POs H,O 
Horn.-gabbro 39.84 o8 19.71 7.73 889 tr. 7.33 13.52 1.59 >53 86 = 100.08 
Uorite 5.5 46.98; .00.. 10,17: | 4.972 67s" Be sos por $i J tr. .o9= 99.84 
Resi se 56.45 tr. 20.15 4.36 5.00 tr. 2.66 6.59 2.95 Roo .24 1.61 = 101.02 
The Rocks Associated with the Iron Ores in Switzerland. — 
Among the rocks associated with the iron ores in Canton Grisons, 
Switzerland, are several that are onene ARPE: according to 
Bodmer-Beder.’ Among them are a diorite, auralite- 
porphyrite, and a quartz-biotite porphyry. The latter has a micro- 
granitic groundmass and large phenocrysts of orthoclase, and smaller 
ones of oligoclase, quartz, and biotite. The groundmass consists of 
quartz and plagioclase, muscovite, zoisite, sericite, sphene, epidote, 
apatite, sillimanite, garnet, magnetite, hornblende, biotite, and second- 
ary substances. Some of the quartz phenocrysts are crossed by 
1 Neues Jahrb. f. Min., etc., Bd. xi, p. 217. 
