ORDER VII. EHOMBOHEDEAL CORUNDUM. 299 



Zn Al 4 , which corresponds to 71'86 of alumina, and 

 28-14 oxide of zinc, not giving attention to the contents of 

 oxide of iron and silica. Alone it is infusible before the 

 blowpipe, and nearly so with borax or salt of phospho- 

 rus. With soda it melts imperfectly into a dark scoria, 

 which being melted again with soda, deposits upon the 

 charcoal an areola of oxide of zinc. 



2. The varieties of the present species generally occur 

 imbedded in talcose slate and quartz, and accompanied with 

 hexahedral Lead-glance and dodecahedral Garnet-blende ; 

 sometimes also with prismatic Gadolinite, dodecahedral 

 Garnet, &c. It is found at Fahlun and Broddbo in Swe- 

 den, and in the vicinity of the Franklin iron-works in New 

 Jersey. 



3. EHOMBOHEDEAL COEUNDUM. 



Rhomboidal Corundum. JAM. Syst. Vol. I. p. 48. Man. 

 p. 148. Corundum. PHILL. p. 74. Saphir. Salamstein. 

 Sclimirgel. Korund. Demantspath. AVERN. Hoffm. H. 

 B. I. S. 541. 547. 561. 565. 572- Korund. HAUSM. II. 

 S. 366. Korund. LEONH. S. 393. Tele'sie. Corindon. 

 HAUY. Traite, T. II. p. 480. T. III. p. 1. Corindon. 

 Tabl. comp. p. 29. Traitd, 2de Ed. T. II. p. 70. 



Fundamental form. Rhombohedron. R = 86 6'. 

 R. G. 



a = V 5-5609. 



Simple forms. R oc (o) ; R (P) ; R + 1 (a) 

 = 68 45'; P + 1 (r) = 128 3', 122 18'; 

 P + 8 (b) = 122 2%, 149 1% ; P + 3 (e) = 

 120 37, 164 2(X ; f P + 1 = 136 47', 94 53' ; 

 J P + 1 (c) = 126 16', 129 5% ; f P + 2 

 = 124 1', 139 40' ; | P + 3 (I) = 121 5', 

 159 IV; |P + 4 = 12017 / ,16930'; R + oc; 



