494 University Geological Survey of Kansas. 
angle B is not 90°, which results agree with those of D’Achi- 
ardi, though the angle could not be measured. Three facts 
- point to this conclusion: (1) The extinction, though appar- 
ently parallel in some cases, is in a great many crystals ob- 
lique; (2) unequal development of dome faces is too often to 
be merely the result of accident; (3) measurements of the 
interfacial angles of dome faces show them to be hemiortho- 
domes, and hence its crystals are monoclinic. 
The crystals occur in radial aggregates showing free ends. 
They are tabular parallel to the clinopinacoid (010). Three 
positive and three negative hemiorthodomes were observed. 
As the angle B is so nealy 90°, they appear as three macro- 
domes of the orthorhombic system. Three kinds of crystals 
were found, as represented in figures 69, 70, and 71. The 
following results of measurements under the cross-hairs of a 
microscope show clearly the monoclinic character of the crys- 
tal; the results are the means of several measurements: 
es I? AS NSA Aly MBO 77 8 BO G2 3’ aA BEV 2 
y’=40° 11’. The crystal represented in figure 81 is of the 
most frequent occurrence. No symbols can be obtained for 
these dome faces if we assume Belar’s ratios. D’Achiardi’s 
original paper was not at hand. If the domes in figure 81 are 
assumed to be (101) and (101), then the others are (203), 
(203), (103), and (103). Besides these forms the basal 
pinacoid often occurs, but as it is small and its combination 
edge with the dome faces rounded, no measurements were pos- 
sible. Thus the angle B and the axial ratios could not be ob- 
tained. A prism, presumably the unit one, occurs, but no 
measurements of it were possible on account of the thinness 
of the crystals. 
The mineral as here described is from the Big Coon mine, 
Galena, where it is associated with cerussite, linarite, caledo- 
nite, malachite, chalcopyrite, and sphalerite. Chrysocolla, 
cuprite and covellite also occur at this mine. 
Aurichalcite has long been known from Granby, where it 
occurs in globular aggregations of the usual bluish-green 
color. The crystals are not as perfectly developed as those 
from Galena. Figure 72 gives an idea of their form. The 
face on the upper end of the crystal from the horizontal line 
