870 The American Naturalist. [October, 
General Notes. 
MINERALOGY: 
Crystallization of Enargite.—Pirsson’ has studied enargite 
from two new Colorado localities, viz., the Ida Mine, Summit District, 
and the National Belle Mine, Red Mountain. At the former locality 
the mineral is deposited in cavities left after the kaolinization of feld- 
spar phenocrysts in porphyry. These crystals are tabular parallel to 
o; Po, and are bounded by the forms œ P®, oP, oP, and œ P». 
At the latter locality two types of crystals are found. One of these is 
in thick, striated prisms bounded by the same forms as the Ida 
Mine crystals and sometimes in addition PX, Poo, oo P;, and another 
brachydome. ‘The second type of crystals from this locality is tabular 
parallel to the base and shows hemimorphic development. The forms 
observed on this type are oP, o» P o», «P, o P5, Px, ł Ps. 
Crystallization of Scolecite and Meta.scolecite.—Rinne' 
has investigated crystals of scolecite from Iceland and shown that the 
mineral erystallizes in the rare inclined-faced hemihedral division of 
the monoclinie system. This fact was developed by etching and bv 
study of the pyroelectric properties. The front faces of the prism 
have different etched figures from the rear faces, while in twinned 
crystals with the twinning plane the ortho-pinacoid, front and rear 
faces of the prism have the same figures. In simple individuals the 
front and rear faces are pyroelectrically positive and negative poles 
respectively. In twinned crystals all prism faces are positive and a 
negative zone follows the twinning line on œ P'zz with neutral bands 
on either side. 
When crystals of the mineral are heated much above 120? C they 
become cloudy, and the crystal structures seems at first sight to be 
lost, but by brightening up in oil it is found that a molecular re- 
arrangement has taken place. This new mineral Rinne calls meta- 
scolecite. The inclined-faced hemihedrism of the monoclinic system is 
retained, but a remarkable revolution of the molecular groups through 
- 'Edited by Dr. Wm. H. Hobbs, University of Wisconsin, Madison, Wis. 
~ *Am. Jour. Sci., (3) xlvii, pp. 212-215. 
?Neues Jahrb. f. Mineral., etc., 1894, II, pp. 51-68.. 
