Tempera- 

 ture °C. 



Time of 

 exposure. 



1140 



8 days 



6 Morey & Bow en — Melting Potash Feldspar. 



Table II. — Results of heating experiments on potash feldspars. 



Microcline. 



Eesult. 



Little change except formation of rare 

 stripes of glass corresponding with 

 original stripes of albite. 

 1179 8 days Abont half unchanged microcline ; other 



half glass showing cross-lining (leu- 

 cite). 



All changed to glass showing cross-lin- 

 ing (leucite). 



All changed to glass and definite skele- 

 tal forms of leucite. 



Glass and definite skeletal leucites, often 

 as rectangular crosses. 



Glass and rounded to subhedral leucites 

 (0.02 mm. diameter) with regularly 

 arranged inclusions of glass. 



Glass and rare subhedral leucites. 



All glass. 



Sanidine and Adularia* 



Mostly unchanged. Small percentage, 

 glass showing cross-lining (leucite). 



About one quarter unchanged feldspar ; 

 rest glass showing cross-lining (leu- 

 cite). 



All changed to glass showing cross-lin- 

 ing (leucite). 



All changed to glass and definite skele 

 tal forms of leucite. 



Glass and minute rounded leucites. 



Glass and very rare minute leucites. 



Glass only. 



a The results obtained with these are practically identical and can be 

 given together as above. 



1204 



8 days 



1252 



5 days 



1307 



3 days 



1400 



3 days 



1435 

 1452 



3 days 

 3 days 



1140 



8 days 



1179 



8 days 



1204 



8 days 



1252 



5 days 



1400 

 1452 

 1465 



3 days 

 3 days 

 2 days 



