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THE AMEBICAN MINENALOGIST
A certain amount of care must be exercisedin placing the
stopper on the pycnometer. The latter having been filled to
overflowing with water (or other suitable liquid) is grasped at
the neck by the thumb and finger of the left hand, and with
the other hand the stopper is pushed on firmly with a sliding
rnotion. Uniess the temperature rises (in which caseno bottle
of this gerreral type is satisfactory), the stopper sticks to the
bottle and is not easily dislodged. The weight of the pycnometer filled with liquid can be determined to within 0.1 mg.'
which implies an accuracyof about 0.0001in the density of an
ordinary mineral. The convenienceas well as the accuracy of
this pycnometer is likely to appeal to any one who is engagedin
determining densitles.
NEW MINERAL SPECIES DESCRIBED DURING 1916-1920.
Eoaen T. Wunnny, Wosluington,D. C.-About sixty mineral specieshave
been described as new during the period from 1916 to 1919 (and early 1920),
inclusive, and published in this magazine, either in the original or in abstracts.
It seemsworth while to present a classificationof these, more or less according
to Danats System of Mineralogy (Ed. 6), so that their relations to previously
known minerals or groups will be brough' out.
The primary subdivisions, or "families," as they may perhaps be called,
are as follows:
A. Native elements, including isomorphous mixtures of elements.
B" Sulfides, selenides,arsenides,etc., and sulfo-salts.
C. I{alides, including oxyhalides and hydroxyhalides.
D. Oxides, including double oxides and hydroxides.
E. Carbonates, oxalates, organic compoundsl also borates.
F. Sulfates, molybdates, etc.
G, Phosphates,arsenates,vanadat'es,etc.
H. Columbates, tantalates, titanates, etc.
L Silicates of all kinds.
The first four of these families are essentially as in Dana; in E, however,
types of compounds are introudced which Dana scatters in various places.
It seems logical to place with the ca,rbonatesall other carbon compounds,
just as all sorts of silicates are grouped together; and borates, which resemble
carbonatesfar more than they do the uranates, with which Dana groups them,
also fit in well here.
The order of the last, four families is exactly reversed from that of Da,na,
the idea being that it js well to take up compounds in the order of increasing
complexity, which brings sulfates early and silicates late. Titanates are
placed with columbates becauseof the striking isomorphism these two types
of compounds show.
13
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