1903.] WRIGHT—CRYSTALLOGRAPHIC PROPERTIES. 248 | 
Pp, 4) belonged to the first type of crystal habit; No. 8 (with ¢, Z, 4) 
to the second ; No. 2 (with ¢, z, v, 5), No. 3 (with ¢, v, ~, 4), No. 
mmr. a, 0, 450 (2)) No. -§ (6,2, 0, fy ay Gyee), NON 6 (c's, 2, 
p, 6) and No. 11 (¢, v, p) to the third, and No. g (with J, 4) to 
the fourth. 
Development of the Crystal Forms.—The only zone of any ccn- 
sequence present is that of the pyramid from the base to the prism. 
Considering the base and prism as primary forces the series reads 
¢, 2, U, p, 6 or 02 1 2 w. This series is normal except for the 
second member 2. The sense of this variation is not apparent. 
The primary forces have produced in the domeykite crystals the 
most common crystal faces. The simple dominant of the series 
v, 10, and the form /, 20, appear equally well developed, while 
the most highly differentiated form z, 2 o occurs least frequently. 
The crystals of domeykite tarnish easily to iridescence, and are 
then unfit for measurement. Luster of fresh crystals splendent 
metallic ; color tin-white to steel-gray in reflected light, black in 
diffused light, often with a tinge of red. Fracture conchoidal, 
uneven. Brittle. Indications of a cleavage or parting after the base 
may result from the leafy texture mentioned above. Cleavage after 
the prism @ (11Z0)) o imperfect but distinctly noticeable. The 
specific gravity was left undetermined, as sufficient material for 
an accurate measurement was not available. 
EtcuH FIGuREsS. 
In these experiments the etch figures on the basal plane only were 
observed. ‘This face is the largest and most perfect, and the one 
best adapted to reveal the crystallographic nature of the mineral. 
The other faces, moreover, occur only as narrow bands, frequently 
striated horizontally—two features detrimental to the formation of 
good etch figures. 
In the process of etching, the minute domeykite crystals were 
placed in a small receptacle or holder made of finely woven plati- 
num wire meshes, attached to which was a long handle of thicker 
wire, and then dipped into the acid, allowed to remain there a 
certain length of time, finally removed by means of the thick wire 
handle and plunged quickly into water. In this manner it was pos- 
1Compare V. Goldschmidt, ‘* Ueber Entwickelung der Krystallformen,” Zez¢s- 
chrift fiir Krystallographie, Bd. xxviii, p. 1-35, 419-451. } 
