4A6 DESCRIPTIONS OF ROCKS. 
the line between the mica-bearing and the hornblende-bearing rocks, 
as here done, and to use the name syenyte for the rock to which it was 
originally applied, as well as for the quartzless kinds. 
2. Syenyte-gneiss.—Like gneiss in aspect and schistose 
structure; and also in constitution, except that horn- 
blende replaces mica. Occurs both with and without 
quartz, though usually quartz-bearing. ‘The varieties are 
nearly the same as under syenyte. Metamorphic. 
3. Hornblende schist.—A schistose rock consisting of horn- 
blende, with usually more or less quartz, but sometimes 
almost wholly hornblende. Frequently contains epidote, 
garnet, magnetite. Metamorphic. 
4. Amphibolyte.—A very tough, granular-crystalline rock, 
consisting of hornblende, and hardly schistose in structure. _ 
Color, greenish-black to black. Metamorphic. 
A Glaucophanitic variety consists chiefly of the blue soda-hornblende, 
called glaucophane, with usually some black mica. From Saxony 
Isle of Syra, New Caledonia. 
5. Actinolyte—A tough, massive rock made chiefly of 
actinolite. Grayish green. Metamorphic. 
6. Unakyte.—A flesh-colored granitoid rock consisting of 
orthoclase, quartz, and much yellowish-green epidote. From 
the Unaka Mountains, North Carolina, and East Tennessee. 
II, CONTAINING NEPHELITE. 
1. Zircon-Syenyte.—A crystalline granular rock consisting 
of orthoclase, microcline, little hornblende, crystals of zir- 
con, and some eleolite. 
2. Foyayte.—Coarse crystalline, granular to compact 5 
consists of orthoclase, reddish-brown nephelite (eleeolite), in 
six-sided prisms, and blackish-green hornblende. Occurs 
also porphyritic, and passes into an aphanitic variety. From 
Mt. Foya and Picota, in the Province Algarve, in Portugal. 
oe (p. 444) is related, but contains very little horn- 
ende. 
5. HORNBLENDE AND SODA-LIME-FELDSPAR SERIES. 
I. NOT CONTAINING SAUSSURITE IN PLACE OF THE 
FELDSPAR CONSTITUENTS. 
1. Dioryte. Quartz-Dioryte. (Greenstone in part. )—The 
triclinic feldspar, one of the acidic (rich in silica) species, 
