664 
MINERALOGY: R. A. DALY 
If Foullon, Grandjean, Triimpy, and Heim are correct in regarding 
these albite and orthoclase crystals as chemically precipitated at the sea 
floor, the formation temperatures must have been well below 100°C. 
If, on the other hand, the crystals developed only after burial of their 
calcareous matrices, the formation temperatures were nevertheless com- 
paratively low. The Paris-basin rocks were never buried more than a 
few hundred meters. Assuming a burial of 1000 meters and the present 
thermal gradient (3° per 100 meters of depth), the formation tempera- 
tures could hardly have reached 100°. Though the burial was deeper 
for other cases (Alberta and the Alps), formation temperatures of much 
more than 200° cannot well be assumed, even if the crystallization were 
delayed until the maximum sedimentary covers were completed. 
In any case the Paris-basin limestones apparently prove that albite, 
orthoclase, and quartz are crystallized in calcareous muds at tempera- 
tures lower than 100° and probably lower than 70°. Since this paper 
was practically completed for publication, it was found that Doelter^'^ had 
already assumed a formation temperature of 'perhaps 100°' for the 
potash feldspars of the Paris-basin Chalk. 
The lowest recorded temperature at which orthoclase has been arti- 
ficially prepared is 300°. That feat was accomplished by Chrustschoff," 
who developed both orthoclase and quartz in an aqueous solution of 
dialyzed silica with alumina and caustic potash, kept for several months 
at the temperature mentioned. Friedel and Sarasin^'- using analogous 
solutions in bombs, produced albite, orthoclase, and quartz in mach 
shorter periods, but they employed a temperature of 500°. These ex- 
periments suggest that time may be one of the important factors aiding 
the crystallization of alkaline feldspars at very low temperatures. 
What the exact chemical conditions for these noteworthy precipita- 
tions in calcareous mud were, is a question now impossible to answer. 
Perhaps the abundance of lime in the muddy matrices affected the solu- 
bility of the alkalies in sea-water one should further consider the pos- 
sible influence of decaying animal matter on the various solubilities in- 
volved. The astonishing concentration of potash feldspar in the Water- 
ton dolomite accentuates the difficulty of the problem. 
1 Heim, A., Beitr. geoL Karte Schweiz, N. F., Lief 20, 1916, (514, 543, 561, 567). 
2 Triimpy, D., Ihid., Lief., 46, 1916, (83, 108). 
' Kaufmann, F. J., Ihid., {Ser. 1), Lief., 24, 1886, (583). 
<Lory, C, Paris, C.-R. Acad. ScL, 103, 1886, (309). 
6 Lory, C, Ihid., 105, 1887, (99). 
fl FouUon, H. B., Sitzher. Wiener Ak., 100, Abt, 1, 1891, (162, 169). 
7 Cayeux, L., Paris Mem, Soc. GeoL, 4, No. 2, 1897, (259, 279, 303, 432-434). F. Grand- 
jean, Paris, C.-R. Acad. Sci., 148, 1908, (723), holds that these potash feldspars described 
