1 8 The American Geologist. January, i904. 
composite parallel growth. At this locality the forms are not 
the prism (no) and second order pyramid (loi) reported by 
J. P. Cooke as occurring on the Rockport, Mass., cyrtolite.* 
The mineral is infusible, los'es color, glows, does not be- 
come magnetic when treated on charcoal and is practically in- 
soluble in hydrochloric acid. The hardness is about six, being 
just marked with steel. The lighter portion appears to be 
softer and less tough than the blacker (core) material. The 
mean specific gravity of three portions of the grayish-brown 
material is 3.5761, and of the brownish-black (core) material 
3.8441. 
A microscopic examination of a thin section showed that 
the material was undoubtedly decomposed and that the change 
from the darker to the lighter portions was due to the progress 
of the alteration and also to the presence in the former of a 
large number of minute black inclusions. These dust-like black 
inclusions are probably uraninite, as the darker portions yield 
much stronger blowpipe tests for uranium than the lighter 
portions. The higher specific gravity of the blackish (core) 
material would also corroborate this theory. 
In view of the evident lack of homogeneity and altered 
character of the mineral, an elaborate quantitative analysis was 
not deemed advisable, especially as the preliminary testing re- 
vealed the presence of uranium and probably of yttrium, in- 
volving very troublesome separations. The following average 
approximate determinations, by E. Waller, proved the mineral 
to be undovibtedly of the type of the described altered zircons : 
SiO, 27.24, ZrOo 53.56. Different samples yielded UoO., 1.14 
to 4.35. Yttrium was probably present and traces of mangan- 
ese, calcium and copper were also noticed. The uranium per- 
centage is unusually high, being due to the black, dvist-like in- 
clusions of uraninite. The Mt. Antero, Colorado, cyrtolite, 
however, shows 4.82 percentage of UoO^.f 
The Bedford mineral strongly resembles the cyrtolite from 
Llano county, Texas, which shows the same rough tetragonal 
crystals with curved faces. $ 
The cyrtolite from Spruce Pine, Mitchell Co., N. C, has 
the same general type of crystals, but the color is much light- 
• American Journal of Science. toI xliii, p. 238, 1867. 
t Zeit. f. Kryst u. Min. xxiii, 597. 
j HiDDBN and Mackbntosh, Am. Jour. Sci., toI. xxxriii, p. 485, 1889. 
