MINERALOGY: G. P. MERRILL 
303 
optical properties further than given in the paper referred to above, sec- 
tions of both the Alfianello and Rich Mountain stones were submitted 
to Dr. F. E. Wright of the Geophysical Laboratory, who reported the 
mineral to be weakly birefracting with interference colors not exceeding 
gray white of the first order, and the refractive indices of which were 
a = 1.623 ± 0.002 and y = 1.627 ±0.002, the birefringence being less than 
0.005. He also verified previous determinations of its biaxial and doubt- 
fully positive character. With these additional data at hand reference 
was made to E. S. Larsen's tables,^ where it was found that the only 
known mineral possessing the properties found by the various observers 
was the phosphate francolite, which is reported, however, as optically 
negative. Nevertheless, with this much for a guide, an attempt was 
then made at ascertaining its chemical nature. The small size of the 
particles and their sporadic occurrence rendered it impossible to isolate 
them either by heavy solution or by an electro-magnet. Recourse was 
then made to micro-chemical methods. After repeated trials, a small 
particle, less than 0.5 mm. in diameter, was removed from an uncovered 
section of the Alfianello stone, and transferred to a clean slide where it 
was covered with a drop of strong hydrochloric acid and allowed to 
stand over night, during which time the acid evaporated to dryness. 
On taking it up again in a fresh drop of acid the mineral was found to 
have been strongly attacked though not completely dissolved. A drop 
of the solution was then transferred to still another slide and placed in 
contact with a drop of sulphuric acid. Abundant acicular and plumose 
crystals of gypsum shortly began to make their appearance around the 
margin of the drop. The liquid remaining on the first slide was then 
evaporated to dryness over an alcohol lamp and the residue taken up 
with nitric acid, a drop of ammonium molybdate solution added, and 
the slide slightly warmed on the steam radiator for a few moments, 
when abundant characteristic globules of the phospho-molybdate of 
ammonium separated out. As checks upon this, independent tests 
were made in slides from the Alfianello, Dhurmsala, Felix, Mocs, and 
Rich Mountain, meteorites by painting around the mineral with vase- 
line and treating the exposed portion with a drop of nitric acid. The 
mineral was found to be completely and easily soluble in this acid and 
in all cases results confirmatory of the first were obtained. It may be 
added that the solution in nitric acid goes on so rapidly that its prog- 
ress may readily be observed under the microscope. In making this 
test, nitric acid has the advantage in that it does not so readily attack 
the olivine and there is hence no trouble from the obscuring reactions 
by gelatinous silica. The tests for other constituents, such as alumina, 
