98 CONTRIBUTIONS TO MINERALOGY. [buli 
the majority of the small sharply defined crystals are probably rui 
They are at times slightly dichroic (yellow to brown), and occm 
equidiametral crystals. Some of the crystals in the bands of sillin 
ite have been crushed and lengthened out. In one case a crysta 
corundum was inclosed in rutile. Zircon is also widely distribute* 
irregular grains, usually of minute size. Occasionally a large p 
has roughly the usual crystal outline, but seems to have been mon 
less corroded. One large crystal inclosed several small rutiles. 
order of crystallization of the minerals seems to have been as folk 
Corundum, rutile (and titanite), zircon, sillimanite, and quartz. It i 
be that there are two generations of sillimanite. Those long, sler 
sharp crystals in the quartz may have formed after the crystals in 
bands. 
An analysis of the rock was made by the writer, giving the res 
tabulated below: 
Si0 2 75. 54 
A1 2 3 18. 65 
Fe 2 3 35 
FeO 06 
Mg( ) none 
CaO 03 
Alk none 
H 2 0— 1.10 
H 2 0-|- 3. 67 
Ti0 2 48 
Zr( ">, 06 
P 2 5 trace 
FeS 2 10 
100. 04 
The large amount of water present is difficult to explain, 
inclusions in the quartz account for some, and assuming the pres( 
of some water due to incipient alteration in the sillimanite. ther 
still a large amount unaccounted for. 
From the analysis, neglecting the water and accessory minerals, 
composition of the rock is calculated as consisting of 
Quartz 69 
Sillimanite 31 
Deducting the water and other accessory minerals of the rock 
obtain the following comparison: 
Analysis CUc ggj 
recalculated. ( . ( J p b ™ 
Si( >, . 
A1 2 3 
