132 S. L. Penjfield—Phenacite from Colorado. 
of 7, over p, to the left; unfortunately the erystal had been so 
attached that the relative size and position of these faces on 
the lower side could not be observed ; on the top of the erystal, 
however, the three alternating faces were large, the other three 
small, as shown in the figure: 0 occurs only to the left of 7, be- 
ing present three times ‘above and three below. Of rhombo- 
hedrons of the third order, « and x, occur under the negative 
rhombohedron, z, both to the right and left, and are about 
equally developed, while s occurs under the positive rhombo- 
hedron r to the right only. These forms have not only the 
same symbols, but also the same position with reference to the 
positive rhombohedron on the Colorado as on the Russian 
phenacites, as shown by a comparison with the figure of 
Kokscharow. 
The remaining crystals, which are to be described, are from 
an entirely new locality, Mt. Antero, in Chaffee Co., about one 
hundred miles southwest of Denver, fifty- five miles from Topaz 
Butte, and sixty-five miles a little to the south of west from 
Pike’s Peak. Mt. Antero is over 14,000 ft. high, and the 
phenacites were found by a prospector (whose name I do not 
know) at one spot on the surface, in a streak up and down the 
steep slope of the mountain and above the timber line, proba- 
bly at an altitude of 12,000 feet. The crystals were given by 
the discoverer to the Rev. R. T. Cross,* of Denver. So far as 
known the country rock is granite, and the associations are 
beryl, quartz and feldspar. The suite of specimens in the 
author’s possession consists of eight specimens of pale, bluish 
green aquamarine, upon three of which the crystals of phena- 
cite are implanted. The crystals are prismatic, and the largest, 
about 7™™ in length, is implanted in an inclined position upon 
the basal plane of the beryl, while others are scattered irregu- 
larly over the prismatic face. The specimens were proba- 
bly not found in place, as the edges of the crystals are more or 
less rounded and nicked, as if they had rolled around in contact 
with other hard minerals. The beryl crystals are deeply 
striated parallel to the vertical axis and eaten out, having per- 
haps furnished the material for the formation of the phenacite. 
The habit of the phenacite crystals is remarkable, and is shown 
in fig. 4 in ordinary projection, and in fig. 5 in basal projection, 
the figures being placed in the same relative position as those 
above. In the prismatic zone the prism of the second order a 
prevails, while m is always small, in some cases wholly want- 
ing. The crystals are terminated mainly by the rhombohedron 
of the third order x, 1322, —r 3-2: The unit rhombohedron 7 is 
small and in a zone between it and the prism @ is the rhombo- 
* Some notes upon this locality by the Rey. R. T. Cross will be found on a 
later page of this Journal. 
