446 DESCRIPTIONS OF HOCKS. 



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. Metamorphie. 



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. Metamorphie. 



4. Amphibolyte or Hornblendyte. — A tough, granular-crys- 

 talline rock, consisting of hornblende, and hardly schistose 

 in structure. Color, greenish-black to black. Metamorphie. 



A Glaucopkaniiic variety consists chiefly of the blue soda-hornblende, 

 called glaucophane. with usually some black mica ; from Saxony. Isle 

 of Syra, New Caledonia. A chrysolific variety occurs at Stony Point, 

 Rockland Co., X. T., and on the opposite side of the Hudson River, 

 north of Cruger's. 



5. Actinolyte. — A tough, massive rock made chiefly of 

 aetinolite. Grayish green. Metamorphie. 



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. 



n. COXTAEsESTG NEPHELITE. 



1. Zircon-Syenyte. — A crystalline granular rock consisting 

 of orthoclase. microcline. little hornblende, crystals of zir- 

 con, and some elsolite. 



2. Foyayte. — Coarse crystalline, granular to compact ; 

 consists of orthoclase. reddish-brown nephelite (eheolite), in 

 six-sided prisms, and blackish-green hornblende. Occurs 

 also porphyritic, and passes into an aphanitic variety. From 

 Mt. Foya and Pieota. in the Province Algarve, in Portugal. 

 Ditroyte (p. 444) is related, but contains very little horn- 

 blende. 



5. HORNBLENDE AXD SODA-LBIE-FELDSPAR SERIES. 



I. NOT COHTAXHmG SAUSSUBITE EH PLACE OF THE 

 FELDSPAE CONSTITUENTS. 



1. Dioryte. Quartz- Dior yte. (Greenstone in part.) — The 



triclinic feldspar, one of the acidic (rich in silica) species, 



