456 University Geological Survey of Kansas. 
observed on but a single crystal. Measurements with the 
contact goniometer are as follows: 
k, \k, 17-6-6 , 17-6-6, 5 measurements, average 53° 19’, 
calculated 53° 3’. 
M,{833!—808. This form is very common, as it is uni- 
versally present on crystals of type 2. It is the form that 
the writer described’ as a new form for sphalerite. The posi- 
tive character of this form was based upon the direction in 
in which the etch-hills described in the list of forms under the 
rhombic dodecahedron pointed on a single large crystal. The 
faces of the tetrahedra were absent on this crystal. Further 
study of crystals on which tetrahedra exist has shown that 
the form is negative, as the faces of the positive tetrahedron 
(identified by its smooth surface) acuminate the solid three- 
faced angle of the three prominent dodecahedral faces. The 
form on the large crystal with the etch-figures may be posi- 
tive, but this seems hardly probable, as in all other par- 
ticulars it agrees with crystals on which the form under 
consideration is certainly negative. The following measure- 
ments were made with a contact goniometer : 
M, ,M, 833 ,833, 12 measurements, average 55° 43’, cal- 
culated 55° 423’. 
n, {322! 808. This tristetrahedron was observed on but a 
single crystal. It is listed by vom Rath’ as an uncertain 
form. Measurements with the contact goniometer are as 
follows : 
Average. Calculated. 
n, jn, 322 ,232,5 measurements, 19° 32’ QS Ausy 
n,ac 3822,100,6 fe ANDO Boy A3Z° 18.14” 
An undetermined hextetrahedron often modifies the inter- 
section edge M,,d on crystals on type 2. 
On one crystal of decided tetrahedrid aspect a hextetrahe- 
dron, the symbol of which could not be determined, exists 
together with the faces of the tetrahedron, the cube, a posi- 
tive and a negative tetragonal trisoctahedron, a positive tris- 
tetrahedron, and a negative tristetrahedron. 
CoMBINATIONS.—The greater part of the sphalerite crystals 
5. Amer. Jour. Sci. (4), vol. IX, pp. 184-186, 1900. 
6. Verh. d. Naturhist. Ver. d. preuss. Rheinlande, Bonn, 1879, 36. 
