KINDS OF ROCKS. 451 



3. Noryte. Hypersthenyte. — A rock consisting of labrador- 

 ite or oligoclase, with true foliated hypersthene ; from St. 

 Paul's, Labrador, Hitteroe, Egersund, Harzburg ; fine 

 grained, in Cortlandt, N. Y., between Cruger's and Peeks- 

 kill. 



4. Doleryte. {Basalt, Trap.) — Chief constituents, labra- 

 dorite and augite, with magnetite, and sometimes anorthite. 

 Often porphyritic, and the feldspar crystals may be anor- 

 thite. Amount of silica yielded on analysis usually 47 

 to 52 per cent. Texture crystalline-granular to aphanitic; 

 and often, especially in the latter, having glassy particles 

 among the crystalline, or even an unindivi dualized base 

 or magma between the crystalline grains — the variety called 

 Basalt ; often coarse granular through the body of a dike, 

 while aphanitic along its walls, and sometimes containing 

 glassy portions in the latter when not elsewhere. Colors 

 dark grayish to bluish-black, greenish-black, and brownish- 

 black. G-. =2 -75-3 -1. Eruptive ; also metamorphic. 



It includes the larger part of the rock usually called trap, abundant 

 inmost regions of igneous eruptions ; constitutes the "trap" ridges 

 of the Connecticut Valley, the Palisades of New Jersey, and similar 

 ridges in Nova Scotia and North Carolina ; also in the Lake Superior 

 region, and extensive beds of so-called basaltic rocks over the Rocky 

 Mountain slopes west of the Front Range. The rock of New Haven, 

 Conn., from West Rock, afforded Silica 51 '78, alumina 14-20, iron ses- 

 quioxide 3*59, iron protoxide 8 •25, manganese protoxide 0'44, magne- 

 sia 7*63, lime 10*70, soda 2*14, potash 0*89, loss by ignition 063, phos- 

 phorus pentoxide 14=99 89; G. =3 03. A hydrous or chloritic variety 

 from Saltonstall's Ridge, near New Haven, afforded Silica 49*28, 

 alumina 15*92, iron sesquioxide 1-91, iron protoxide 10*20, manganese 

 protoxide 037, magnesia 5*99, lime 7*44, soda 3*40, potash 0*72, water 

 390, carbon dioxide 1*14=100*72 ; G.=2*86. 



Vabieties. — There are two series : A. Ordinary, B. Ghrysolitic, 

 and for the latter the name Peridotyte has been used. Each occurs : 

 a. anhydrous ; b. hydrous, or chloritic, of feeble lustre; c. amygda- 

 loidal, as well as chloritic ; d. vesicular, or scoriaceous, as in doleritic 

 or basaltic lavas. Spilite is amygdaloid. 



Again, each of these varieties may be porphyritic. Again, the augite 

 may be in distinct crystals. 



A coarse- granular kind, having the pyroxene foliated, is sometimes 

 called gabbro. 



This basic rock, doleryte, is often called, also, basalt, especially 

 when it has an unindividualized base ; a specimen of this kind, from 

 Nevada, i3 represented in fig. 7, page 418. The name, anamesite, 

 has been used for an aphanitic kind, but is unnecessary. 



Diabase. — The term diabase is very often applied to doleryte older 

 than Tertiary. It was formerly supposed that the former differed from 

 the latter in being chloritic, and. afterwards in never containing glassy 

 particles or an unindividualized base ; but neither distinction holds. 



