THE MINERALOGRAPHY OF THE FELDSPARS 289 
2. The thermo-equilibrium diagram of the iron-carbon binary 
system offers the mineralogist a method of studying the alloys which 
Liquid 
SOLUTION 
SOLID SOLUTION 
bed 
& 
= 
= 
q 
(° 4 
ry 
a 
= 
fed) 
- 
M90 80 70 60 50 40 30 20 
PERCENTAGE COMPOSITION 
Somes 
Fic. 18.—Thermo-equilibrium diagram of a eutectiferous, limited-solubility 
system. The general type probably represented by the potash-soda series. 
