KINDS OF ROCKS. 89 



have been included under this name. Some that have been called trap are 

 here included. 



2. Augitic or Basaltic Series. 



95. (1.) Diorite. — Similar to the metamorphic diorite, but usually the horn- 

 blende less abundant and the feldspar less finely developed. Color, grayish 

 white. A variety consisting of hornblende and anorthite constitutes some of 

 the dikes of Canada. (T. S. Hunt.) 



(2.) Dolerite ( Trap, in part). — Texture crystalline-granular to cryptocrys- 

 talline (the fine variety often called anamesite). Color, dark gray, greenish and 

 brownish black. Consists of labradorite and augite, with often magnetic iron. 

 Sometimes columnar. G. = 2.75-3. 



Porphyritic dolerite. — Speckled with crystals of feldspar, or with feldspar and 

 augite, or with augite alone. 



Amygdaloidal dolerite. — Containing nodules of zeolites, chlorite, quartz, or 

 calcite. Includes much of the so-called amygdaloid. 



Another variety contains the augite in black crystals. 



Doleritic lava. — Structure scoriaceous or very cellular. 



(3.) Basalt. — Like dolerite, but less granular than the coarser dolerite, and 

 containing also chrysolite in grains looking like green glass. Compact. Often 

 columnar. G. = 2.9-3.2. 



Porphyritic basalt. — Speckled with crystals of feldspar. 



Amygdaloidal basalt. — Containing amygdals of zeolites, etc. ($ 68). 



Basaltic lava. — Scoriaceous or very cellular. The lava may be porphyritic 

 with feldspar or augite crystals. 



(4.) Letjcitophyr. — A dark-grayish, fine-grained, cellular volcanic rock, con- 

 sisting of augite and leucite with some disseminated magnetic iron. It is the 

 lava of Vesuvius. The leucite is either in whitish grains or in trapezohedral 

 crystals (see $ 57), and is disseminated like the feldspar crystals in a 

 porphyry. 



(5.) Nephelinite (N'ephelin-dolerite). — A crystalline, granular volcanic rock, 

 consisting of nepheline and augite, with some magnetic iron, the nepheline 

 partly in distinct crystals. Color of the coarser kind, grayish or whitish ; 

 of the finer, dull ash-gray. 



The tufas and conglomerates of volcanic regions are noticed on p. 74. 



Wacke is an earthy rock made of basaltic earth partially compacted, — a kind 

 of tufa. 



(6.) Basaltic Obsidian. — The massive obsidian of Kilauea, Hawaii, a region 

 of basaltic lavas, contains 22 per cent, of protoxyd of iron, and the capillary 

 (Pele's hair) 30 per cent. The light scoria of the crater is an impure volcanic 

 glass, very much inflated. 



