74 LITHOLOGICAL GEOLOGY. 



quartz-dioryte ; containing quartz in disseminated grains. The porphyritic varieties in- 

 clude dark red and brownish-red ancient porphyries, as well as dark green kinds, and 

 may also be quartzose; they have been called porphyrite. 



2. Labradioryte (Labradorite Dioryte). — The feldspar, one of the basic (poor in 

 silica) species, labradorite or anorthite. Texture usually fine-grained, sometimes 

 cryptocrystalline. Color light grayish-green to dark olive-green, blackish-green, or 

 gray, and sometimes black. Very tough. Sp. gr. =2-8-3-l. Often contains chlorite 

 and also magnetite. Often has associated with it beds of serpentine or ophiolvte. 



Varieties. —a. Granular crystalline, b. Compact, or finegrained, of dark green 

 color; constituent minerals not distinct, c. Porphyritic; the feldspar in whitish or 

 greenish-white crystals disseminated through a fine-grained base, making a greenish 

 "porphyry." d. Pyroxenic ; containing some disseminated pyroxene, e. Magnetitic. 



3. Contain a triclinic feldspar and pyroxene or hypersthene as the prominent constituents. 



1. Gabbro {Gabbro, in part, Hyperite).— A basic granitoid rock in part, consisting 

 of cleavable labradorite with disseminated pyroxene, or a granular crystalline aggre- 

 gate of the two minerals. The pyroxene often in a lamellar state, improperly called 

 hypersthene. In place of labradorite, the feldspar is sometimes andesite, and sometimes 

 anorthite. Color, dull flesh-red to brownish-red, also dark-gray to grayish-black. 

 Tough. Sp. gr. 2-7-3-1, varying with the proportion of pyroxene, which is some- 

 times small. Contains also magnetite or titanic iron. 



The name gabbro has been applied to this rock; also to a coarsely granular igneous 

 rock, consisting chiefly of labradorite and foliated pyroxene, referred beyond to doler- 

 yte; to euphotide; and, by the Italians, to a diallage-bearing serpentine. Ferber, in 

 his "Briefe" (1773), says (p. 98) Gabbro, of Florence is the same as the rock called 

 "sachsischen Serpentin, in Deutschland," that is, the serpentine of Zoblitz. 



Varieties. — a. Granitoid ; the feldspar in distinct cleavable grains or masses, b. 

 Feldspathose ; the pyroxene feeble in amount, c. Chrysolitic ; contains disseminated 

 chrysolite in addition to the other ingredients, d. Anorthitic, or Tractolite; anorthite 

 replacing the labradorite. 



Another rock$ also called gabbro, has the aspect of euphotide (page 75), into which it 

 graduates ; but the compact whitish or greenish base, instead of being saussurite, is 

 true labradorite (its sp. gr. about 2*7). The other chief constituent is light green sma- 

 ragdite, which is a lamellar variety of hornblendt, but sometimes partly or wholly 

 pyroxene. Occurs with the euphotide of the Alps. 



2. Noryte (Hypersthenyte). — A rock resembling the preceding, consisting of cleav 

 able labradorite with true foliated hypersthene. 



4. Consist mainly of hornblende or pyroxene. 



1. Hornblende Schist. — A schistose rock consisting mainly of greenish-black 

 hornblende with usually some quartz or orthoolase. 



Varieties. — a. Quartzose; consisting of hornblende and quartz, b. Epidotic. c- 

 Garnetiferous. d. Micaceous. Graduates into 



2. Amphibolyte or Hornblendyte. — A very tough, granular-crystalline rock, 

 consisting of hornblende, and hardly schistose in structure. Color, greenish-black to 

 black, often Garnetiferous ; sometimes Chrysolitic. Graduates into 



Aphanite, a cryptocrystalline hornblende rock of black color. Aphanite is ill part a 

 cryptocrystalline dioryte. 



3. Actinolyte. — A tough, massive rock made chiefly of actinolite. Grayish green. 



4. Pyroxenyte. (Augite Rock). — Coarse or fine granular pyroxene rock. 



4. Garnet, Epidote, and Chrysolite Rocks. 



1. Garnetyte, or Garnet Rock. — A yellowish-white to greenish-white, tough 

 rock, consisting of an alumina-lime garnet. Sp. gr. 3 - 39-3*49. From St. Francis, 

 Canada. The yellow whetstone of Vieil Salm, Belgium, has the composition of garnet. 



2. Eclogyte. — Compact and tough. Consists of granular garnet and hornblende, 

 with gras?-green smaragdite. Sp. gr. 3 -2-3-5. A related rock consists of reddish 

 or brownish-yellow garnet, and black or greenish-black hornblende, with often some 

 magnetite. 



