ic RADE a a Kd ae eae eee, 
ik , i 4 : i pe 
š J á 
642 General Notes. fJuly, d 
by crystal planes. They enclose glass areas which are derived 
from original inclusions, and contain also fluid inclusions with 
movable bubbles. Tridymite is much more rare under these con- 
ditions than quartz. It is usually found lining cavities around 
the periphery of glass particles or veins, and is generally free 
: rom inclusions. The granitic feldspar is likewise in many cases 
surrounded by a rim of “ neogenous” feldspar, which frequently 
builds around the original irregular fragment a completely devel- 
oped crystal. The newly-formed feldspar is much less opaque 
than that from which it was derived, and contains fewer inclu- i 
sions. Among those that occur are little fluid cavities contain- 
3 
í 
7 
ing movable bubbles. A most instructive portion of the paper 1s 
that which treats of the experiments which were undertaken by | 
the author to explain the origin of the secondary fluid inclusions, i 
and to find the conditions under which the silica separated out in i 
crystal form. Pöhlman’ has recently described biotite-gneiss, 
; quartzite, olivine-kersantite and nepheline-basalt from the north- 
í ern part of Paraguay. The olivine-kersantite contains, in a dark 
| gray ground-mass, large crystals of biotite (meroxan), perfectly 
fresh augite and flesh-colored pseudomorphs of olivine, These 
pseudomorphs consist of serpentine, very pleochroic bunches of 
a micaceous mineral, carbonates and iron oxides. According 
to Carl Ochsenius,? the blue color of much of the Strassfurt salt 1s 
not due to sulphur, but is merely an optical effect. 
MINERALOGICAL News.—Emmonsite, a new mineral from neat 
Tombstone, Arizona, has been described by W. F. Hillebrand. 
It is of a yellowish-green color, translucent, and occurs in “ad 
talline scales and patches in a brownish gangue composed of lea 
angles to each other: Against one of these the extinction IS 
8°-12°. Pleochroism very slight. Specific gravity about 5. 
se allowing for impurities the mean of four analyses was 45 
ollows : 
Te Se Fe H,O 
se 58.75 0.53 14.29 above 3.28 
„It is most probably a hydrated ferric telluride. Twins of we 
nabar“ have been found in the recently discovered ore deposits 1 
_ the neighborhood of Bachmut, Ekaternioslaw, South Russi® 
: The crystals are inter-penetration twins with the base the twin 
ning plane and the twinning axis the vertical axis. The planes 
_ 1 Neues Jahrbuch fiir Min., etc., 1886, 1, p. 244. 
_ *Ib., p. 177. 
__ * Proceedings Colorado Scientific Society, Vol. 11, Pt. 1, 1885, P- 1- 
‘“Ischermak. Miner. u. Petrogr. Mitth., vil, p. 361. ; 
