448 DESCRIPTIONS OF ROCKS. 
oligoclase or andesite and hornblende, with G.=2:73—2:80, and afford- 
ing 55 to 61 per cent. of silica ; it occurs in the Peak of Teneriffe, on 
Liscanera I. near Stromboli, and on some parts of Etna. Another rock 
included under this name, found at Stromboli, Rceca Monfina, and 
Tunguragua in Quito, contains augite in place of hornblende, with 
oligoclase or labradorite, and is near doleryte. A third rock deseribed 
under this name by Ludwig is augitic trachyte, the feldspar being 
sanidin. Trachyte graduates into andesyie, augite-andesyte, doleryte, 
as well as granite. ; 
3, Labradioryte. (Labradorite-Dioryte, Greenstone in part. ) 
—'T'he feldspar one of the basic (poor in silica) species, la- 
bradorite or anorthite. Texture usually fine-grained, some- 
times crypto-crystalline. Color light grayish-green to dark 
olive-green, blackish-green or gray, and sometimes black. 
Very tough, G.=2°8-3'1. Often contains chlorite and 
magnetite. Often has associated with it beds of serpentine 
or ophiolyte. Metamorphic and eruptive. 
VARIETIES.—a. Granuiar crystalline. b. Compact, or fine-grained ; 
of dark green color; constituent minerals not distinct. ec Porphyri- 
tic ; the feldspar in whitish or greenish-white crystals disseminated 
through a fine-grained base, making a greenish ‘‘ porphyry ;” its 
crystals sometimes anorthita d. Pyroxenic ; containing some dissem- 
inated pyroxene. e. Magnetitic ; containing magnetite or titanic iron, 
Occurs in the Urals ; to the west.of New Haven, Conn., both massive 
and porphyritic ; in Littleton, N. H. A porphyritic varicty of the 
rock near New Haven—a metamorphic rock —afforded Hawes, Silica 
48°61, alumina 17°81, iron sesquioxide 0°25, iron protoxide 8°46, man- 
ganese protoxide 020, iime 11°15, magnesia 7°76, soda 2°77, potash 
0°47, water 1°63, titanium dioxide 1°35=100°17; G.=301. A com- 
pact non-porphyritic variety from the same formation, collected on 
Steeckel’s farm, afforded Hawes, Silica 50°36, alumina 14°57, iron ses- 
quioxide 2-48, iron protoxide 8°31, manganese protoxide 0°46, magne- 
sia 7°62, lime 11°18, soda 3°04, potash 0:44, water 0°78, titanium diox- 
ide 1°70, chromium oxide 0°78=100°89 ; G.=3°04. The crystals of the 
porphyritic variety, according to an imperfect analysis by E. 8. Dana, 
consist of anorthite. 
4. Corsyte-—A granitoid rock, consisting chiefly of anor- 
thite and hornblende, with some quartz and biotite. From 
Corsica. 
Teschenite is bluish-green, and chiefly consisis of anor- 
thite, hornblende, and augite, the hornble de sometimes in 
large black prisms ; also contains analcite. From Teschen, 
Austria. : 
5. Isenite.—Contains a triclinic feldspar and hornblende, 
with much nephelite and nosean, and some magnetite. 
From the Hisbach (Isena) district in the Westerwald, West 
Germany. 
