296 The American Geohxjist. November, 1897 
not been observed. The crystal form indicates that apatite 
was one of the earliest minerals solidified; nevertheless, in 
an area highly altered, apatite needles are so thickly crowded 
as to suggest at least, a secondary origin. 
10. Sphene, or titanite, is in small amount; it has gener- 
ally a rough crystal outline, the crystals being so small that 
the biaxial character was determined only after considerable 
search. Two cleavages were observed, as well as fracture. 
The pleochroism frequently passes into a shade reminding one 
of the flesh color of garnet. 
11. Tourmaline is identifiable in isolated spots in very 
limited amount. It occurs in hexagonal crystal form as well 
as in shapeless aggregates. The pleochroic colors are a very 
pale blue and a dark grayish blue without a trace of the or- 
dinary violet shade. This is an interesting fact, inasmuch as 
tourmaline has been found at only oneother place in Minne- 
sota.* 
12. Pyrite occurs in very minute quantities. Only two 
grains were large enough to give a really satisfactory color 
in reflected light. Some of the smaller grains appear to be 
decomposed; they may be some other iron ore. No distinct 
crystal outline was observed, 
13. Calcite exists in small microscopic grains, as a decom- 
position product of the feldspars. Only a few grains have 
been noticed, and the identification is not entirely satisfac- 
tory. 
14. Zoisite is about as abundant as apatite, and would 
therefore naturally be mentioned before sphene and tourma- 
line, but its determination has been so uncertain tluit it has 
been relegated to this rank. In ordinary light its appearance 
closely resembles that of epidote, with which it is associated 
in origin and occurrence. The crystals are, however, much 
smaller, and show the characteristic blue-gray interference 
color. 
15. Muscovite is thought to occur in very small quantity. 
Only two or three microscopic grains were noted. The few 
distinguishable characters agree with thf)se of muscovite. 
16. One more mineral deserves mention. It is a large mi- 
croscopic twin of a green, strongly pleochroic substance. The 
*Namely, at Pipestone rapids, leading into Basimenan lake. 
