pULLER.] 
MINERALOG1CAL NOTES. 
143 
The difference in the (f* and f> angles, for the forms, calculated from 
he two values, differ not more than a minute. 
The average value obtained by Melczer is 
p o =.7309 
q o =.7027. 
Taking the average of all three sets of values, we have 
Po- 
Qo- 
.7308 
-. 7311 
. 7309 
.7014 
.7019 
.7027 
Av., .7309 
Av., .7020 
The axial ratio for libethenite then becomes 
a:b:c = .9605 : 1 : .7020. 
21. CRYSTALLOGRAPHY OF LEPIDOLITE. 
A group of lepidolite crystals was collected by the writer in the 
ummer of 1904 at a gem mine about 4 miles east of Ramona, on the 
tage road from Ramona to Julian, San Diego County, Cal. The 
nine was opened and worked for its gems, such as topaz, tourmaline, 
garnet, etc. With these are associated quartz, orthoclase in good 
rystals at times several feet long, muscovite, and, rarely, lepidolite. 
?he minerals in question all occur in the loose dirt, tilling "pockets" 
^i a pegmatite dike. 
; The specimen of lepidolite under consideration consists of a group 
I intergrown crystals which often reach large size. The group itself 
I about 5 cm. thick and the individual crystals measure about 1 cm. 
pross the base, though crystals with a diameter of 2 cm. are not rare, 
'he crystals are also proportionally thick, the average being from 2 to 
i mm., though a few are somewhat thicker. They are transparent 
nd of a ver} T pale pink color, and, in the direction normal to the ver- 
bal axis and parallel to the base, of a slightly deeper tint. The}^ fuse 
ksily to a white enamel, coloring the flame an intense crimson. The 
jde faces are usually plane, not rounded nor striated, and of a brilliant 
plish, giving excellent signals. It is, however, extremely difficult to 
pure a complete crystal from the group owing to the perfect basal 
ieavage, which will cause a crystal to split into a number of layers, 
his will also at times cause part of a crystal to become slightly dis- 
laced. In consequence of this difficulty most of the crystals meas- 
red are only parts of the original crystals, and two such pieces 
