948 Th American Naturalist. [November, 
ance of dust inclusions scattered through it. The special features of 
the gabbros are the reaction rims around pyroxene and magnetite. A 
zone of small brown hornblendes is often found between the first named 
mineral and plagioclase. Between magnetite and feldspar are usually 
three zones, of brown hornblende, pink garnet, and quartz, respectively, 
the last named mineral occurring nearest the feldspar. Sometimes the 
order of the zones is different. The quartz may appear within the 
zone of garnets, in which case the latter mineral may replace the feld- 
spar in part, as alternate lamellae between lamellae of plagioclase. 
The gabbros contain large bodies of titaniferous magnetite. On the 
contact of the eruptive with limestone the latter rock has been crystal- 
lized and silicified. The same author, associated with Marsters,’ has 
described the trap dykes of the Lake Champlain region as camptonites, 
fourchites, monchiquites and bostonites. 
The Augite Granite of Kekaquabic Lake, Minnesota.— 
The granite of Kekaquabic Lake in Northeastern Minnesota, occurs 
in granitic and in porphyritic phases, according to Grant.’ In both 
varieties the constituents are quartz, anorthoclase and other feldspars, 
augite, a little hornblende, biotite, apatite and sphene. The granitic 
variety needs no further mention. In the porphyritic phase the quartz 
and feldspar form a fine grained groundmass in which lie phenocrysts 
of feldspar and augite. An analysis of this feldspar, whose density is 
2.58-2.62 gave: 
SiO, ALO; Fe, d MgO KO Nao HO Total 
67.99 19.27 8 02 3.05 623 .90 — 99.03 
The augite comprises from 5-20 per cent of the rock. Its tint varies 
from green to colorless, the lighter colored portion often lying within 
a darker outer zone. Analysis of the augite yielded: 
SiO, AlO, FeO FeO CaO MgO K,O NajO H,O Total 
19 2.38 925 5.15 17.81 943 .38 263 .01— 10033 
The rock, which is an augite soda-granite, has the following composi- 
tion : 
SiO, ALO, FeO, FeO CaO MgO K,O Na,O H,O P,O, Total 
66.84 18.22 2.27 20 331 81 2.80 5,14 46 tr = 100.05 
5BullU S. Geol. Survey, No. 107. 
7Amer. Geol., XI, 1893, p. 383, 
