2p8 1 lie American Geologist. November, lyot* 
sesses perfect cleavage parallel to the base, and in sections 
parallel to the base the pleochroism is scarcely perceptible ; in 
other sections it is strong with: 
;/g --- clear brown. 
Hm = reddish brown. 
Tip -^ pale yellow. 
The absorption is //m > n^ > ;/,,_ but n^^ and n^ are nearl\- 
equal. 
The refringence is high and the birefringence very strong: 
)Ur — //p -050 at least. 
The mineral is negative and often very nearly uniaxial, but 
sometinmes 2E is as large as 5° 42' (measured by 2.d). 
No percussion figure has been obtained, but the cleavage 
fragments parallel to the base frequently show a separation 
plane which must be parallel to ^'(010), and occasionally near- 
ly complete hexagons occur, through the presence of parting 
probably parallel to b'^'''^{\\\). Repeated examination shows 
that the optic plane is always perpendicular to the easiest plane 
of separation g^{o\o), and the mica is therefore the rare va- 
riety anomite. 
The anomite encloses rounded and subangular grains of 
cordierite, sometimes showing its characteristic twinning, and 
bronzite. It contains more rarely crystals and needles of 
magnetite, masses of pyrite, crystals of apatite and zircon. 
Around the last two, greenish pleochroic halos are usually de- 
veloped, especially intense around zircon. A remarkable 
halo is represented in Fig. 16. It is developed in biotite along 
its contact with enstatite. Many other similar contacts show 
no sign of halo, but one other analogous occurrence has been 
noted, 
Cordierite is not at all uncommon in the noryte. but since 
it is wholly colorless and devoid of the pleochroic halos com- 
monly found in it . its determination is a m.atter of considerable 
difficulty. As it has never before been reported in granular 
igneous rocks of the labradoritic series, it deserves special 
attention. Crystal outline is quite common, but the angles are 
always rounded, and formless grains are abundant. The faces 
observed are : p{oo\)Jt^{\o&), g\o\6), /7%(iii), and as twining 
faces: ;//(iio) and ^"(130). 
Cleavasres are vers- rare, if not entirelv absent. This cor- 
