332 The American Naturalist. [ April, 
Pearceite is monoclinic; à: b:¢’==1.7309:1:1.6199; @=89° 51’. 
The crystals have usually a hexagonal aspect. They are black in 
color with metallic lustre, hardness 3, and specific gravity about 
6.15. It is suggested that the high percentage of copper—more than 
18%—may account for the opacity of pearceite. It is very easily fus- 
ible and gives readily test reactions for its component elements. The 
pearceite specially studied occurs with quartz, calcite and chalcopyrite 
at the Drumlummon mine, Lewis and Clarke Co., Montana. 
A careful study of the crystal form of polybasite leads to the conclu- 
sion that it also is monoclinic instead of orthorhombic or rhombohedral 
as previously supposed. The axial ratio à : b : c'—=1.7309 : 1; 1.5796 ; 
=O". 
Perhaps the most interesting part of the paper is the comparison of 
pearceite and polybasite with each other and with certain other more 
or less allied minerals. From this it appears that arsenic compounds 
have a slightly longer vertical axis than the corresponding antimony 
minerals. Five cases are cited to illustrate this. Attentiou is also 
called to the fact that the prismatic angle is nearly 60° as a rule, and 
that in this respect chalcocite, Cu,S, and stromeyerite, Cu AgS, closely 
resemble the sulpho-salts. 
Miscellaneous Notes.—Davison" gives the name Wardite to a 
mineral which appears from a partial analysis to consist largely of a 
hydrous basic phosphate of aluminum. It occurs with the Utah vari- 
scite, and may be allied to turquoise and peganite——More careful 
study of the percussion figure of the micas by Walker’ discloses the 
fact that the angle between the rays varies in some instances very con- 
siderably from 60°. Muscovite showed an angle of 52° 53’ to 55° 57’, 
lepidolite 59° 7’ to 60° 12’, biotite about 60°, and phlogopite 60° 52’ 
to 63° 28’. On five crystal fragments of the mineral leonite, MgK, 
(SO,),+4H,0, Tenne? determined its crystal form to be monoclinic, 
with the axial ratio 4: b : ¢'=1.03815: 1: 1.23349, and @==84°50'. This 
is a considerable variation from the crystal form of blédite, which has 
the analogous composition Mg Na, (SO,), + 4H,0. The latter mineral 
is also monoclinic, but its axial ratio is à : b : e- =1.3494: 1: .6715, and 
B=79° 16’. 
7 Am, Jour. Sci., CLII, pp. 154, 155, 1896. 
8 Am. Jour. Sci., CLII, pp. 5- 
® Zeitschr. d. D. biol. Ges., XLVII, ie 632-637, 1896. 
