PHYSIOGRAPHY. 119 



Prehnite. 



2. Analysis. 



ByKLAPROTH. ByWALMSTEDT. By LATJGIER. 



fr. Cape of Good Hope. fr. Dunbarton. fr. the Palatinate. 



Silica . 43-85 . . 44-10 . . 42-50 



Alumina . 30-33 . . 2426 . . 28-50 



Lirae . 18-33 . . 26*43 . . 20-40 



Oxide ofiron . 5-66 . . 074 . . 3-00 



Water . 1-83 . . 4-18 . . 2-00 



Potash and soda 00 . . 00 . . 0-75 



3. It occurs in veins in granite, gneiss, and sienite ; but is more com- 

 mon in balls, irregular veins and vesicular cavities in trap. 



4. It was first brought to Europe by Col. PREHN, from the Cape of 

 Good Hope, in bright colored apple-green varieties. The crystallized 

 varieties come from the Alps of Savoy and Dauphiny. Massive and 

 imperfectly crystallized specimens occur at St. Gothard in Switzerland, 

 in the Tyrol, in Salzburg, Carinthia, in the Pyrenees, in Norway and 

 Sweden. It occurs in considerable quantity near Glasgow in Scotland, 

 also at Reichenbach near Oberstein in the Palatinate, and in the Faroe 

 Islands. In the United States, handsomely crystallized and massive va- 

 rieties, of a rich green color, are found at Farmington, (Conn.) in trap. 

 Others, less beautiful, are found occasionally throughout the trap region 

 of Now England and New Jersey. It occurs in veins in gneiss, at Bel- 

 lows Falls, (Vt.) and at Charlestown, (Mass.) in sienite. 



PRISMATOIDAL CoPPER-GLANCE. 



Primary form. Right rhombic prism. 



Secondary form. The primary, having the acute lateral edges 

 truncated, and the acute solid angles so deeply truncated, as to 

 produce dihedral summits. 



Cleavage parallel with the secondary literal planes, rather per- 

 fect, though interrupted. Fracture imperfectly conchoidal. Sur- 

 tace rough. 



Lustre metallic. Color blackish lead-grey. Streak unchan- 

 ged. 



Brittle. Hardness =3-0. Sp. gr. =5-735. 



Compound Varieties. Massive : composition granular, indi- 

 viduals strongly connected. 



1. Before the blow-pipe, it gives nearly the same results as Bournon- 

 ite, with which it appears to agree in chemical composition. 



