<5 LITHOLOGICAL GEOLOGY. 



or wholly wanting. It commences in the granite-like hyperite, 

 consisting of crystallized feldspar (usually labradorite) and hyper- 

 sthene. It passes into the tough and compact euphotide. 



The hornblendic series blends laterally with the inagnesian series, especially 

 through the chloritic rocks of the latter, chlorite being near hornblende and 

 pyroxene in composition, though containing water. It also blends with the 

 mica series through granites and. schists that contain both hornblende and mica. 

 Through the pyroxenic varieties it also passes into the igneous series. 



(1.) Syenite. — Eesembles granite, but contains in place of mica 

 the mineral hornblende, which is in cleavable grains and either black 

 or greenish black in color. The feldspar may be orthoclase or oligo- 

 clase, and sometimes the quartz is nearly wanting. 



(2.) Hyperite. — Granite-like in texture, and of rather dark color, 

 consisting of cleavable labradorite ($ 55, d, usually dark and dull in 

 color, either grayish, reddish, or brownish, with bright-colored 

 internal reflections) and hypersthene (a lamellar cleavable variety of 

 pyroxene, $ 65 [14] ). A common rock in the Azoic of northern 

 New York and Canada. 



(3.) Diorite, or Greenstone. — Resembles syenite in appearance and granular 

 crystalline texture, but contains little or no quartz : it consists of hornblende 

 and albite or oligoclase (a triclinic feldspar). The rock is therefore whitish, 

 speckled with black or greenish black. It is very tough. Sp. gr. 2.7-2.9. Gra- 

 duates into a compact cryptocrystalline rock of a whitish, grayish, or greenish 

 color. 



Porphyritic diorite has the feldspar in distinct imbedded crystals. Dioritie 

 schist is a diorite rock containing some mica and having a schistose structure. 



(4.) Hornblendic Gneiss. — Eesembles gneiss in schistose structure, 

 but contains hornblende in place of mica. Zircon-syenite is a syenite 

 or hornblendic gneiss containing zircon with its other constituents. 



(5.) Hornblendic 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 contains epidote, and is therefore an 

 epidotic hornblendic schist. 



(6.) Hornblende Rock. — A very tough, granular, crystalline rock, consisting 

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



(7.) Actinolite Rock. — A tough rock made of interlacing fibres of actinolite. 

 Color, grayish green. A variety from St. Francois, Canada, afforded T. S. Hunt 

 (Logan's Report for 1853-56, p. 445) — Silica, 52.30, magnesia, 21.50, protoxyd 

 of iron, 6.75, lime, 15.00, alumina, 1.30, oxyd of nickel, a trace, water, 3.10 = 

 99.95. 



(8.) Pyroxenite (Cherzolite, Augite Rock). — Coarse or fine granular pyroxene 

 rock, consisting of granular pyroxene of a green, grayish green, to brown color, 

 often streaked or clouded with darker or lighter shades of color. Often con- 

 tains, or is associated with, quartz, talc, steatite, and calcite. 



