448 Gustav Rose on Greenstone [Dec. 



and at the gold- washing station of Cavellinski near 

 Miask. 



Frequently the crystals ofuralite have a nucleus of augite 

 possessing a grass-green colour, and whose cleavage faces 

 are parallel with the outer faces of the crystals of uralite. 

 The substitution of the mass of hornblende for the augite 

 is similar to the above described substitution of the horn- 

 blende masses for hypersthene and diallage. Hence, it is 

 probable that the hornblende which occurs in union with 

 this last substance, is also uralite. The union of augite and 

 uralite is found very distinct in the augite porphyry of Mul- 

 dakajeusk, near Miask, in Ural. But also other distinct 

 crystals of augite, as in the augite porphyry of Nicolajeusk, 

 are combined on the upper face with small prisms of horn- 

 blende, or if it be admitted, they have been changed into 

 the latter. Iron pyrites occurs interspersed through the 

 augite porphyry. Quartz, in crystals and grains, as well as 

 hornblende, with its peculiar form, and without combina- 

 tion with agite, appears, as in the hypersthene rock and 

 gabbro. 



With regard to the proportion of the constituents, the 

 augite and labradorite of the augite porphyry are similar to 

 the albite and hornblende of the dioritic porphyry. Augite 

 porphyry occurs, which contains both constituents in nearly 

 equal quantity, but more frequently either the labradorite 

 or augite is present in the greater proportion. The crystals 

 in the augite porphyry lie generally irregularly ; in the 

 labradorite porphyry the crystals are arranged in a some- 

 what regular manner, having their broad lateral faces, or 

 at least, their main axes, parallel, (needle porphyry of South 

 Norway). The crystals appear needle-form, when the frac- 

 ture cuts the axes at right angles, and broad splintery, when 

 it goes parallel with the broad lateral faces of the crystals. 



The principal masses of augite phorphyry are frequently 

 amygdaloid, when quartz is met with, never occurring both 

 in crystals and grains (Holmestrand, in South Norway, and 

 green labrador porphyry ; zeolite and calcspar also some- 

 times occur, (Tyrol) and Pistazite (Tyrol and Tscharysch in 

 Altai). Some varieties of augite porphyry occur, which it 

 is not easy to fracture, and it is usually difficult to obtain 

 from them portions of the size of a common book. Such 



