70 LITHOLOGICAL GEOLOGY. 



Syene, in Egypt, where the rock occurs. When like gneiss in struc- 

 ture, it is called (1 b) Syenytic Gneiss. 



(2.) Hyposyenyte. — Like syenyte, but containing little or no 

 quartz. (2 b) Zircon-syenyte is a similar rock containing zircon. 



Some writers on rocks restrict the name Syenyte to the rock without quartz, here 

 named hyposyenyte, and call the other a variety of granyte. But this is contrary to 

 original use; moreover, it separates syenyte from the hornblendic series, where it be- 

 longs, and with whose species it is usually associated, especially in Archaean regions. 



(3.) Dioryte. — Granular-crystalline, of a grayish-green to dark-green color; con- 

 sists of hornblende and oligoclase or albite (a triclinic feldspar); very tough. Sp. gr. 

 2 - 7-3 - 0. Graduates into a compact cryptocrystalline rock, of a grayish or greenish 

 color. A slaty kind (3 b) is called Dioritic slate. It graduates sometimes toward dia- 

 base and chloride slate. A kind (3 c) containing the feldspar in isolated crystals is 

 Porphyritic Dioryte. A kind (3 d) containing anorthite has been called Anorthite- 

 dioryte ; but it is more properly an Anorthite-diabasyte. 



(4.) Hypeksthenyte. — Granyte-like in texture, and of rather dark color, consist- 

 ing of cleavable labradorite (p. 54), usually dark and dull in color, either grayish, 

 reddish, or brownish, with often bright-colored internal reflections) and hypersihene (a 

 lamellar cleavable variety of pyroxene. Common in northern New York and Canada. 

 Noryte of Scheerer (not of Esmark) is a similar rock. 



(5.) Diabasyte. — Fine crystalline-granular, of grayish-green to dark-green colors. 

 Sp. gr. 2 - 7-2 - 95. Consists of labradorite, with sometimes oligoclase or anorthite, and 

 pyroxene (or hornblende?) and also some chlorite. There is also (5 b) a Porphyritic 

 Diabasyte. It graduates on one side into dioryte, and on the other into chlorite slate. 

 It passes also into a compact kind (5 c) almost flinty in fracture, which is called 

 Aphanyte, sometimes called horn-rock ; or into (5 d) an Aphanytic Slate. 



(6.) Hornblende Schist. — A schistose rock consisting mainly of greenish-black 

 hornblende with some feldspar; another variety, of hornblende and quartz; another is 

 nearly pure hornblende ; another is epidotic. 



(7.) Hornblendyte. — A very tough, granular, crystalline rock, consisting of horn- 

 blende, and hardly schistose in structure. Color, greenish-black to black. 



(8.) Actinolyte. — A tough rock made of actinolite. Color, grayish green. 



(9.) Py'roxenyte (Augite Rock). — Coarse or fine granular pyroxene rock, con- 

 sisting of granular pyroxene of a green, grayish green, to brown color, often sireaked 

 or clouded with darker or lighter shades of color. 



(10.) Lherzoly'te. — Consists mainly of pyroxene, enstatite or hypersthene, and 

 chrysolite. (From L. Lherz.) 



(11.) Ossipyte. — Coarse crystalline-granular, like a syenyte, but consisting of lab- 

 radorite and chrysolite with some kind of hornblende, and titaniferous magnetite. 



(12.) Unakyte. — A coarse syenyte, in which green epidote replaces hornblende. 

 (Unaka Mountains, North Carolina and East Tennessee.) 



3. Felsitic, Epidotic, and Garnet Rocks having the mass or base com- 

 pact (cryptocrystalline.} 



These felsitic rocks may be simply feldspathic, or the base may be partly horn- 

 blendic or quartzose. When they contain hornblende, garnet or epidote, it is apparent 

 in the higher specific gravity. (1.) Some of the light-colored rocks included are trans- 

 lucent and very tough, and contain grass-green diallage (called also smaragdite) in 

 laminae; these are called euphotides: they consist of feldspar, hornblende, epidote, or 

 garnet. (2.) Others are opaque and often dark -colored, and usually contain crystals of 

 feldspar disseminated through the mass; these are porphyries. (3.) The rocks con- 

 stituting the base of the euphotides without the diallage are called felsytes or petro- 

 silex. 



