662 
MINERALOGY: R. A. DALY 
5. All ten of the authors who have reported on the rocks mentioned 
agree that the albite or orthoclase has crystallized in situ without any 
help from metamorphism. Foullon, Grandjean, Trlimpy, and Heim 
definitely express the view that the feldspars developed, as chemical 
precipitates on the sea-floor before or immediately after the burial of the 
corresponding laminae of sediment by the younger laminae. According 
to Cayeux, Lory held the same belief for the orthoclase crystals of the 
Jurassic limestones. The consensus of opinion is, then, that the au- 
thigenic feldspars and quartz attained their full growth well before 
normal diagenesis was completed, that is, while the calcareous muds were 
still unconsolidated. 
These European researches are important from several points of view. 
For students of sediments they indicate a group of facts and problems 
which have been almost wholly untouched in American laboratories. 
They seem to throw light on the origin of an important dolomite in 
the Rocky Mountains. Finally, they furnish proofs of the crystalliza- 
tion of albite and orthoclase at temperatures much lower than have 
generally been assumed as possible. 
In order to complete the summary of the recorded cases, that of the 
Rocky Mountain dolomite may be noted. It appears to represent the 
only known American parallel to the peculiar European limestones. 
The dolomite, named the Waterton formation, was discovered in 1905 
by the writer,^ at Waterton lake just north of the boundary between 
Montana and Alberta. The formation, at least 60 meters thick, is the 
lowest exposed member of the great Rocky Mountain geosynclinal and 
is overlain by 4000 meters of other sediments referred to the Beltian 
(and probably Cambrian) series. Many hundreds of meters of still 
younger strata overlay those rocks before the composite geosynclinal 
was finally upturned, in the Tertiary era. The whole sedimentary cover 
on the Waterton dolomite was probably more than 6000 meters in thick- 
ness; yet the dolomite is lacking in signs of metamorphism, even that 
of the static kind. Igneous metamorphism can be excluded with equal 
definiteness. 
The dolomite is chiefly composed of carbonate grains, which average 
about 0.02 mm. in diameter and seldom reach 0.05 mm. in diameter. 
These grains either interlock or occur as sharp rhombohedra, represent- 
ing the crystal form so characteristic of true dolomite. Many laminae 
of the rock, up to 1 mm. or more in thickness, are charged with dissemi- 
nated grains of glass-clear orthoclase, 0.01 to 0.05 mm. in diameter and 
without good crystal form. A few irregular grains of quartz, with simi- 
lar dimensions, are usually associated. Other laminae are very rich in 
