MAGMATIC DIFFERENTIATION OF IGNEOUS ROCKS 645 
a stage above its melting-point, accordingly in the liquid phase. 
But the rocks normally contain so little FeS, that in the granites, 
syenites, etc., it does not secrete until below the melting-point 
of the mineral, consequently directly in the solid phase. 
ON THE EARLY CRYSTALLIZATION OF “‘APATITE AND ORES’’—OR 
OF THE ‘‘TELECHEMIC’”’ MINERALS 
All phosphates (apatite and monazite with zenotime in granite- 
pegmatite dikes), sulphides (pyrite, pyrrhotite, chalcopyrite, 
pentlandite, etc.), zircon, corundum, spinel, chromite (in peridotites), 
hematite (and ilmenite and magnetite in the acid igneous rocks), 
titanates, tantalates, and niobates (the last ones in granite-pegmatite 
dikes), further carbon (graphite, diamond) and native metals (nickel- 
iron, platinum), as is well known, belong to the very first products 
of crystallization’ in the igneous rocks. All these substances occupy 
an exceptional position, being extremely little soluble in silicate 
magmas at a temperature somewhat above the beginning of 
crystallization of the silicates, and this independent of their melting- 
points (very high in corundum and spinel; medium-high for 
instance in fluorine-apatite, about 1650°; chlorine-apatite, about 
1530°; hematite, about 1560°; and probably somewhat lower 
for instance in titanite, and for pyrrhotite only 1183°). 
For all these early crystallizing minerals, which in chemical 
respect diverge very considerably from the composition of the silicates, 
I have in “Die Sulfid-Silikatschmelzlosungen”’ proposed the term 
““telechemic” minerals (rfXe, tele=distant, the same root as in 
telegram, telephone, telepathy, etc.). 
ON ‘‘REACTION RIMS’’ 
We choose for an example the coronation of olivine bordering on 
plagioclase, described from oliviniferous gabbros, etc., by several 
earlier investigators, with an inner zone (adjoining the olivine) 
consisting of hypersthene, and an outer zone (adjoining the plagio- 
clase) consisting of hornblende almost always associated with some 
amount of spinel. In addition there occurs exceptionally a third 
t For the pyrrhotite we must change the term crystallization to segregation (to a 
special fluid phase). 
