and Augites in fragmental and eruptwe rocks. — 387 
blende which are corroborative of, and add something to, the 
observations made by Becke. The rocks in which these new 
growths have been found are altered diabases. In some speci- 
mens of these rocks the augite has largely changed into horn- 
blende. In these cases in a portion of the individuals of augite 
the alteration of the augite is partial, while in the other portion 
itis complete. Ordinarily, as described by Irving,* Williams 
and others, a single individual of hornblende has resulted from 
one of augite, the two having the usual definite crystallographic 
relations. ‘To this secondary hornblende the new hornblende 
has attached itself. There are here, then, two hornblendes, one 
of which is paramorphic to the augite, while the other is a new 
growth. The added hornblende has founa room for itself, as 
in the case described by Becke, by penetrating the surround- 
ing feldspars. Similar new hornblende is also found inclu- 
ded in the partly decomposed feldspar in numerous small, 
fibrous, independent individuals. The new hornblende is 
of a pale green color; it-is not strongly pleochroic; it shows 
often distinctly its intersecting prismatic cleavage. ‘The crys- 
tallographic continuity of the paramorphic and new _ horn- 
blendes, when the two are contiguous, is as plain as in the case 
described and figured by Becke, where, however, the first 
hornblende seems to have been original. 
In other diabases from the same region the greater part of 
the augite is unaltered. Here nearly every individual of this 
mineral is surrounded by a sheath of hornblende. This horn- 
blende has clearly formed subsequently to the consolidation of 
the rock, as is shown by the following facts: The hornblende 
cuts into the surrounding feldspar in the most irregular manner. 
The augite cores have the forms common in many diabases, 
being bounded by well-defined broken right lines, or lines some- 
what curved, as the spaces left by the feldspars allowed.+ 
Often the new growth has continued farther in places than 
in adjoining ones, and, as it went on, it has sometimes 
widened out, forming within the feldspar club-shaped pro- 
tuberances of hornblende. 
In longitudinal sections (fig. 3) the hornblende is more 
plentiful at the extremities of the individuals than at the sides. 
*R. D. Irving, this Journal, July, 1883, and Feb., 1884. Geology of Wisconsin, 
vol. iv, p. 663. 
M. EK. Wadsworth, Notes upon the Geology of the Iron and Copper Districts of 
Lake Superior. 
G. H. Williams, this Journal, Oct. 1884, and Bull. U.S. G. S., No. 28. 
Frederick H. Hatch, Min. und Petr. Mitth., vol. vii, pp. 75-87. 
+ In the greater number of these rocks the major part of the feldspar has crystal- 
lized prior to the augite, although in certain of them the augite and the feldspar 
mutually interfere to such an extent as to indicate that the augite began to crys- 
tallize before the feldspar had proceeded far in crystallization. 
