636 ST. HL VOGT 
of apatite, and in other places a crystal of apatite serving as Fix- 
kérper for a deposit of pyrite, showing that the two minerals were 
formed practically simultaneously. At the same weight (as o.1- 
0.25 per cent) of apatite, pyrite, and spinel, the crystallization 
of apatite and pyrite seems to commence at a somewhat earlier 
stage than the crystallization of spinel. 
Fic. 34.—From an ilmenite-norite from Storgangen, near Soggendal, Norway. 
Three crystals of pyrite on which have been deposited small crystals of spinel, lying 
in ilmenite. (40:1.) 
ae 8 
Fic. 35.—From a uralitic quartz-norite from Flaad, Evje, Norway. Black= 
pyrite, white=apatite. (40:1.) 
PYRITE AND PYRRHOTITE 
According to the precision-investigations by E. T. Allen, I. L. 
Crenshaw, and I. Johnson,’ at the Geophysical Laboratory in 
Washington, the melting-points are for FeS, 1170+ 5°; for pyrrho- 
tite, 1183° (to 1187°). 
The analyses of phyrrhotite show, as is well known, a surplus 
of S above the proportion Fe:S, which the investigators mentioned 
(1912) interpreted to indicate that some S entered as a solid solution 
inFeS. Soon after, Docent C. W. Carstens,? of Trondhjem, pointed 
out that what enters in the solid solution must be FeS, and not S, 
an interpretation which, independently of Carstens’ statement, 
t Amer. Jour. of Sci., Vol. XX XIII (1912). 
2 Norsk geologisk tidsskrift, Vol. IIL (1914). 
