62 
Troost on i/ie Tyroxene. 
sometimes in granular or imperfect lamillar nodules, 
having a vitreous lustre ; it exists also in small crystals 
or grains disseminated in the modern lavas. 
This Pyroxene offers various appearances in the dif- 
ferent volcanic substances which have not been altered by 
fire. At Vesuvius, where the masses thrown out of the 
volcano are very abundant, this Pyroxene is sometimes 
in small brilliant crystals in the cavities of these substan- 
ces ; sometimes it forms granular masses intermixed with 
Isocrase, Garnet, Mica, Carb. of Lime, Amphigene, So- 
dalite, Metonite, &c. Among substances of the same ori- 
gin, which exist in the volcanic tufas near Rome, at Fres- 
cati, and Tivoli, this Pyroxene is in large rough crystals 
of a dark green colour, and agglutinated with Mica or Am- 
phigene, of which the stone cutters of Rome form small 
ornamental vases, which are sometimes very pretty, ow- 
ing to the chatoyant occasioned by the Mica. The vol- 
canic sands of the shores of the lakes Albano, Nemi, Bra- 
ciano, &c. abound with small crystals of green Pyrox- 
ene often so transparent as to be mistaken for pondota; 
they are not rare in the volcanic sands near Andernan. 
3. Resinous V. Pyroxene Besinoide,HdLuy;Co7ichoi- 
dal Augite^ Jam. It is black, greenish brown, or brown- 
ish olive green, with a resinous lustre — its fracture is imr 
perfectly conchoidal, it is opaque, or sometimes slightly 
translucent. It occurs mostly in Basalt and ancient la- 
vas ; it is in grains of various sizes, seldom larger than a 
hazle nut. These small grains when black are easily 
mistaken for the ferruginous oxide of titanium, which 
substance also occurs in ancient lavas. It is found in the 
Basalt of Fulda in Stessia, and in the volcanic substan- 
ces of the Vogelgeberge, and Basalt of Kaisersthal in 
Suabia, &c. The Schlackenblende of Mr. Noze, which 
