12 
of one lava flow* and was covered by a later lava flow. According to him, 
the phosphate minerals and bitumen have probably resulted from guano 
or other organic material by a process of distillation in situ occasioned by the 
heat of the lava. Without consulting Mr. Hanson, the writer had arrived 
at the same conclusion, and would say further that careful prospecting in 
similar geological horizons will probably be rewarded by the discovery of 
deposits which might have more favourable commercial chemical com- 
position (that is to say — freedom from iron, magnesium, and alumina). 
Other Identified Minerals Associated with the Phosphates and 
the Brecciated Andesite 
VIVIAN ITE 
Vivianite occurs sparingly in several specimens as a thin crust on 
wavyjveinlets of quercyite. It probably has been derived from quercyite 
through the action of iron-bearing solutions. 
PYRITE 
Small cubes of iron pyrites were recognized in several specimens of 
andesite. 
OLIVINE 
Olivine is an important constituent of a basalt collected in the vicinity 
of the phosphate occurrence. 
CALCITE 
Natrolite, heulandite, and chalcedony were observed filling geodes 
which are abundant in the andesite associated with the phosphate-bearing 
vein. 
QUARTZ 
Some quarts crystal aggregates of common habit, a few millimetres 
long, coat the quercyite-collinsite nodules. They appear to be older than 
the asphalt. 
OPTICAL PROPERTIES OF CHEMICALLY ANALYSED 
FERROPREHNITE FROM ADAMS SOUND, 
BAFFIN ISLAND 
Although prehnite is a common mineral and often has been described 
and analysed, very little data regarding its refractive indices have so far 
been published. Johannsen, Larsen, Winchell, Iddings, Dana, and others, 
in their text books give the same indices and apparently derived them 
from the work of Levy and Lacroix on prehnite from Ratschinges, Tyrol. 
These indices are as follows: 
a = 1*616,0 = 1-626,7 - 1-649. 
