1883.] Mineralogy. * 75 
verized rock is suspended, and its constituents separated succes- 
sively according to their specific gravity. 
Another method, recently employed with success, depends 
upon the attractability of ferruginous minerals by an electro-mag- 
net. The poles of a horseshoe electro-magnet are moved about 
through the pulverized substances, the strength of the magnet 
being increased at each succeeding experiment by the ad- 
dition of greater battery power. Thus magnetite and hematite 
may be first extracted by a weak current, then follow ferruginous 
augites, hornblendes and garnets, while a stronger magnet attracts 
tourmaline, idocrase, bronzite, actinolite, etc., and, finally, by a 
still more powerful magnet, biotite, chlorite, muscovite, and even 
dolomite may be extracted. Minerals containing very minute 
percentages of iron may be attracted if tne magnet is powerful 
enough. The gray powder of syenites and diabases may thus be 
separated in a few minutes into a white powder containing the 
non-feldspathic minerals, and a dark-colored one composed of the 
other constituents. 
By employing the former method in conjunction with this, very 
accurate results may be reached. ~ j 
A fhonolite, for example, consisting of orthoclase, nephelite, 
augite and magnetite, was first freed from magnetite by a weak 
magnet, then, the strength of the current being increased, a mix- 
ture of augite and nephelite was extracted, which was finally 
separated into its constituents by the specific gravity method, 
mercuric iodide of proper density being employed. The com- 
position of the rock was thus fourd to be, magnetite 4 p. c., augite 
Il p. c., nephelite 48.5 p.c., orthoclase 25.5 p. c., impure feldspar, 
etc. i Lip c: i 
AXINITE FROM BETHLEHEM.—Through the medium of the late 
Professor W, T. Roepper, Pennsylvania mineralogists have been 
Bethlehem, Pa., the locality having been discovered by Professor 
suggested the name of the species. They occur with asbestos in 
a hornblendic rock, and, while devoid of the beauty possessed by 
Specimens of the same mineral from other localities, are of some 
crystallograthic interest, as lately shown by B. W. Frazier, of 
Bethlehem. A close relationship has been found to exist between 
the crystallograthic characters of axinite and those of datolite. 
The axial lengths closely correspond, and a comparison of the 
angles between similar planes shows a remarkable agreement. 
They. are found, moreover, to correspond in habit as well as in 
angles. Both minerals are silicates of lime and contain boracic 
acid, and it is very probable that the morphological resemblance 
is consequent upon a resemblance in chemical composition. _ 
