^^^9-] Mineralogy and Petrography. 527 
ber of forms occuring upon them. Interpenetrating crystals 
with the twinning axis normal to ooO, consist of modified 
cubes, which are brought into such a position by twinning 
that the striations on parallel cubic faces cross each other at 
right angles. Other crystals contain on their cubic faces stri- 
ations that appear to be discontinuous. The crystals are 
probably contact tronis with 00 O 00 the composition face. The 
crystals from Summit county occur in almost ideal perfection 
in a mass of kaolin in the vicinity of Monte Zuma. Aiaban- 
dite from the Queen of the West mine in Summit county, 
manganite from Devil's Head, Douglas county, crystals of 
dioptase ( 00P2 and — 2R) from near Riverside, P.O., Arizona, 
2.ndi garnets ixoxxv Chaffee county, Col., are also described by 
the same mineralogist. Repeated trillings of vanadinite from 
the Alice mine, Yuma county, Arizona, consist of crystals 
united by their prismatic faces and therefore resembling simple 
crystals. These groups of three crystals sometimes enclose a 
hollow triangular space running longitudinally through the 
center of the group. \vi d. \o1 oi wulfenite crystals from the 
Red Cloud mine in Yuma county were found a {^^x tronis with 
the composition plane ooP. They produce elbow shaped 
forms with the two limbs bent at right angles to each other. 
Fine quarts and epidote crystals, all of the latter of which are 
twinned parallel to ooP occur in pockets in a peculiar rock 
composed of epidote, calcite and pyroxene, overlying a stratum 
of limestone at Calumet, Col. Some new facts are stated re- 
garding the phenacite from Mt. Antero, and a new locality for 
the mineral is mentioned as existing half a mile distant from 
the locality already known. In the second place, the phena- 
cites have a rhombohedral habit in consequence of the devel- 
opment of a rhombohedron of the third order. The pocket in 
which these crystals are found contains also many Baveno 
twins of white microline upon which most of the phenacite 
was implanted. — The feldspar of the nepheline and lencite 
basamites of Kilimandjaro examined by Fletcher a year or 
so ago' has been re-examined by Hyland'. The fresh mineral 
is pearl-gray in color, with a light vitreous lustre. Crystals 
containing the faces oP, ooP 00 are twinned parallel to ccP 00, 
with this face also as the combination plane. In some of these 
an interior, twinned nucleus is surrounded by a zone of un- 
twinned material, which can be removed from the former by 
