380 The American Naturalist. [April, 
MINERALOGY AND PETROGRAPHY:' 
Description of the New Rock Type, Malchite.—The new 
rock, malchite, referred’ to a few months ago as the granitic dyke form 
of diorite, is now described in some detail by its discoverer, Osann 
It forms dykes cutting granite in the Odenwald, Germany. Ina dense 
groundmass are rare phenocrysts of dark mica, pale green plagioclase 
and quartz. The mica is biotite and the plagioclase labradorite. In 
addition to these the microscope reveals the presence of idiomorphic 
green hornblende, allanite and sphene. The groundmass in which 
these lie strongly resembles that of some tinguaites, with hornblende 
and quartz in place of aegerine and nepheline. It consists of a fine 
granular aggregate of feldspar and quartz, the latter with occasional - 
idiomorphie contours, and prisms of hornblende imbedded in the 
aggregate, the prisms often arranged in flowage lines. An analysis of 
a fresh specimen of the rock yielded: 
_ SiO, AI,O, Fe,O, FeO MgO CaO Na,O K,O.H,0 SO, P,O, Total 
63.18 17.03 .24 637 92 417 4.44 2.91 .52 .19 .283—100.20 
The Petrography of Hokkaido, Japan.—In a general geo- 
logical sketch of Hokkaido, (Jezo or Yesso), Japan, Jimbo‘ declares 
that the island consists largely of paleozoic beds, probably underlain 
by amphibolites and various other schists, and cut by granite, diorite, 
gabbro, peridotite, and serpentine. In the lower portion of 
the paleozoic the beds consist largely of pyroxenites, with traces of rad- 
iolarian remains, phyllites, quartz-schists, limestone, and serpentine. 
The pyroxenites are aggregates of light colored augite, quartz and 
feldspar, in which the augite is often more or less changed to epidote 
and glaucophane. Where the granite cuts the clastics the clay slate 
is changed by contact action to a biotitic clay slate, to hornfels and to 
mica schist, with the latter nearest the eruptive. Tourmaline occurs in 
the schist and cordierite in this rock and in the mica slate. An 
amphibolite in the contact belt is supposed to be an altered tufa. 
Schistose granites, diorites and gabbro are phases of the corresponding 
- Edited by Dr. W. S. Bayley, Colby University, Waterville, Me. 
s CAN NATURALIST, May, 1892, p. 422. 
> . 380. 
‘General Geological sketch of Hokkaido, with special refer€nce to the petrography. 
Satporo, Hokkaido, Japan, 1892. 
