278 DESCRIPTIONS OF MINiRALS. 
Cleavelandite is a lamellar variety occurring in wedge- 
shaped masses at the Chesterfield albite vein, Mass. “f 
Obs. Albite occurs in some granites and gneiss, and is 
most abundant in granite veins. Fine crystals occur at 
Middletown and Haddam, Conn., at Goshen, Mass., and 
Granville, N. Y. ; Unionville, Delaware County, Penn. 
The name albite is from the Latin aldus, white. 
Miicrocline. 
A potash-feldspar, very close to the following species in 
angles, and also in physical characters, and identical with it 
in composition. But it is very slightly triclinic, the angle 
between its cleavage planes varying but 16’ from 90°; and 
hence its cleavage surface shows usually the fine striations 
exhibited with rare exceptions by all the triclinic feldspars. 
Colors white, flesh-red, copper-green. The last is what has 
been called Amazon-stone ; as heat destroys the color it has 
been supposed to be of organic origin. - 
Occurs in the zircon-syenyte of Norway ; also in the Urais ; 
Greenland; Labrador; Everett, Mass. ; Redding, Conn.; 
Delaware ; Chester County, Penn.; White Mountain Notch, 
green ; Pike’s Peak, Amazon-stone ; Magnet Cove, Ark. 
Orthoclase.—Common Feldspar. 
Monoclinic ; and hence angle between the cleavage planes 
90°. Figures 1 to 4 represent common forms, and 5 to 8 
twin crystals. Usually in thick prisms, often rectangular, 
and also in modified tables. Also massive, with a granular — 
structure, or coarse lamellar ; also fine-grained almost flint- 
like in compactness. Colors ight; white, gray, and flesh- 
red common ; also greenish and bluish-white and green. 
Composition. K,Al10O,,Si, = Silica 64:7, alumina 18:4, 
potash 16°9=100. Soda sometimes replaces a portion of 
the potash. B.B. fuses with difficulty ; not acted on by 
acids. 
Common feldspar includes the common subtranslucent 
varieties ; Adularia, the white or colorless subtransparent 
specimens, a name derived from Adula, one of the highest 
peaks of St. Gothard. Sanidin or glassy feldspar includes 
transparent vitreous crystals, found in trachytes and lavas; 
but some of the ‘‘ glassy feldspar” belongs to the species 
anorthite. Lozxeclase is a grayish variety with a pearly or 
greasy lustre that contains much soda. 

