414 
MINERALOGICAL GEOLOGY 
production of borax must entirely cease. South American and 
Asiatic fields take its place. It is a fight to the death between 
America and Europe for the control of a world market. 
Keyes. 
Possible Secondary Character of Bedded Colemanite. When the 
question of the genesis of colemanite in thick nodular layers of 
crystal first came up in connection with the Daggett, Death Valley 
and Lang deposits a likelihood of formation of the borate through 
replacement of limestone early presented itself. The negative 
behavior of ordinary chemical reactions, as carried on in the labor¬ 
atory, offered no serious objections because of the fact that in 
bittern lakes the multitude of complex salts so often present made 
almost anything possible. A deterring factor militating against 
any limestone replacement theory was the circumstance that no 
regular limestones appeared in close association in the borate bear¬ 
ing deposits; no undoubtable proofs of such a transition revealed 
themselves; the geological phases of the problem seemed to be all 
against it; the hypothesis was reluctantly discarded despite the 
fact that it appeared to be so necessary. 
At a later date, the independent revival of Gale’s hypothesis of 
the replacement of limestone, although so spectacular, multiplied 
so vastly the difficulties previously met with that his arguments 
for the acceptance of his contention only more strongly clinched 
the reasons for its rejection. In the meanwhile, another sugges¬ 
tion of origin was made. A proposal for playa genesis of the 
colemanite through change of original ulexite raised some new 
considerations. Since beds in which the colemanite occurred were 
not playa deposits at all the likening of them to the latter was 
manifestly entirely fanciful. Ingenious as was this argument, and 
not withstanding the fact that it offered the best evidence against 
itself, it was the means of casting a new light upon the problem of 
opening the replacement hypothesis for review. 
In the mile-thick succession of sediments in which the colemanite 
beds are incorporated there is, as already intimated, wonderful 
diversity of origin. It is doubtful whether any area of like size 
on the face of the earth presents like variety of formational con¬ 
ditions. Portions, perhaps the most of them, are maritime in 
character; some are manifestly shallow-water accumulations; bit- 
