408 DETERMINATION OF MINERALS. 
ALBITE, p. 277, OLIGOCLASE, p. 276. H.=6; G.=2-56-2:72; 
triclinic, but cryst. as in orthoelase, except that the two cleavage 
planes make an angle of 954° to 94°, and one of them has the surface 
striated ; white usually, flesh-red, bluish ; B.B. fuse with a little 
difficulty ; not acted on by acids. 
LABRADORITE,, p. 276. H.=6 ; G.=2°66-2°%6 ; triclinic, like albite 
in cryst., and nearly in cleavage angle, 93° 20’, and in striz# of 
surface ; white, flesh-red, bnh red, dark gray, gyh brown; B.B. 
fuses easily ; decomposed by HCl with difficulty. 
ANORTHITtTE, p. 275. H.=6-7; G.=2°66-2°78; cryst. and striz 
as in albite, cleavage angle 94° 10’ ; white, gyh, rdh; B.B. fusion 
difficult ; decomposed by HCl with separation of gelat. silica. 
MICROCLINE, p. 278. Very near orthoclase in all characters, but 
triclinic, cleavage angle differing only 16’ from a right angle, and 
surface of most perfect cleavage striated, but strizs exceedingly 
fine, often difficult to detect with a good pocket lens, and requiring 
the aid of a polariscope ; color white, gray, flesh-red, often green. 
For optical distinctions of FELDSPARS, see p. 274. 
BUCLASE, p. 288. H.=%:5; G.=8'1; in monoclinic crystals, with 
one perfect diagonal cleavage ; pale green to white, bah; trans- 
parent ; becomes electric by friction. 
