112 CONTRIBUTIONS TO MINERALOGY. [bull. 26S| 
The cleavage is — macropinacoidal good, prismatic {210} imperfect, 
and basal imperfect, and perhaps, also, in traces, brachypinacoidal. 
The New York mineral shows the macropinacoidal cleavage very well, 
while the California mineral shows the imperfect basal cleavage. The 
fracture is rough and the fibrous prisms are somewhat brittle, though 
a mass of fibers is very tough. The hardness is 7. 
The following values for the specific gravity^ have been given: 
3.36 
3.265 
3.22 
3.319 
3.226-3.13 
3.211-3.302 
Av. 3.292 
The writer obtained 3.306 as the density of a piece weighing about 
10 grams. A good average value would be 3.30. 
The luster is vitreous, somewhat satiny on the fibrous California 
mineral. The color is usually blue, though also lavender and greenish 
blue to black. The colors noted are: 
France: Blue, black. 
Germany: Blue, bluish green. 
Sweden: Blue. 
New York, Arizona, Washington: Blue. 
California: Lavender. 
The mineral is usually opaque in its massive form, but the .small 
fibers of the California mineral are transparent to translucent. 
OPTICAL CHARACTERS. 
All the determinations made on the mineral from different localities 
have given the same orientation. The axial plane is parallel to the 
brachypinacoid, the acute bisectrix is normal to the base. The mineral 
is negative. 
The following are the pleochroisms noted on the mineral from dif- 
ferent localities: Colorless to cobalt blue, pale yellow or colorless to 
cobalt blue, colorless to pistachio green, colorless to rose salmon, 
colorless to deep carmine, colorless to red purple (California). 
AXIAL ANGLES. 
On the Norway mineral, 2V Na was determined as about 35 . Linck 
states that the angle is somewhat less than that of muscovite. 
