564 The American Naturalist. [June, 
black ; zinc and tin, unaltered. The method is of special importance 
in distinguishing arsenic and antimony compounds, and in determin- 
ing zinc, thallium, and telluric acid. 
Use of Phosphorus in Studying Minerals of High Refrac- 
tive Index.—Retgers* uses colorless to yellow phosphorous as a 
medium in which to imbed small mineral grains, which, because of 
their high refractive-index would appear black if imbedded in Canada 
balsam. Melted phosphorous has a very high refractive index 
(np=2.075) and if used in grains of the size of a pin head can be 
handled without danger. Such a grain is heated on an object glass 
till fusion begins and quickly compressed under the cover glass. The 
substance remains long fiuid in the capillary space and consolidates 
clear and transparent. Rutile, brookite, and anatase are the only 
rock-making minerals of higher index than the phosphorous and these 
are brought out more clearly by it. Ifthe mineral grains to be exam- 
ined are so coarse that there is considerable danger of the oxidization 
of the phosphorous, the latter may be dissolved in carbon bisulphide. 
It is much more convenient to work with the solution but its maximum 
index is considerably lower than that of the fused metal. 
Chalcocite from Monte Catini.—Boeris® has investigated some 
specimens of chalcocite from the Monte Catini mines, Lucca, Italy. 
On these crystals he has made out five forms new to the locality 
4 (230), (012), (023), (021), (111) }, and one (052) which is new to 
the mineral. Another new form (270), though very small, was deter- 
mined with considerable probability from its zones. There is also de- 
scribed a new twinning law for the species, the twinning plane being a 
face of (011). 
Diopside and Apatite from Zoptau.—Griiber® describes this 
new locality for diopside and apatite. The former appears in crystals 
up to 5 cm. long, which have terminations conditioned by the forms z 
(021), p (101), u (111), and s (111). The crystals are bright grass 
green and translucent. The crystals of apatite are thick tabular and 
3-1 cm. long, and are either colorless or of a pale amethyst color, 
They occur loose in clay and in a much weathered horneblende schist. 
In addition to the base, first order prism, and first and second order 
pyramids, two-third order pyramids, » (1231) and (1341) are found 
on the crystals. 
* Neues Jahrb. f. Mineral., etc., 1808, m a. 130-134. 
5 Zeitsch. f. Kryst:, xxiii, pp. 235-23: 
*Tscherm. Min. u. Pet. Mitth., xiv To pp. 266-270. 
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