ORDER vin. DI-miSMATIC IRON-ORE. 415 



Fundamental form. Scalene four-sided pyramid. 

 P = 139 37', 117 38', 77 16'. Vol. T. Fig. 9. 

 HAUY. 



a : b : c = 1 : V 5 ' 1428 : ^2-2857. 



Simple forms. P QD ; P (o) ; P + o> (M) 

 = 112 37'; (Pr + oo) 3 = 78 28'; Pr (P) 

 113 2'; ?r + oo. 



Char, of Comb. Prismatic. 



Combinations. 1. P. P -f- QD. 2. Pr. P + oo. 



3. Pr. P. P 4- oo. Fig. 4. 4. Pr. P. 



P -f oo. (?r + QD) 5 . All of them from Elba. 



Cleavage, Pr and P + oo indistinct, more easily 

 observed P oo and Pr 4- oo. Fracture im- 

 perfect eonchoidal, uneven. Surface streaked, 

 of the vertical prisms parallel to the axis, of the 

 rest of the faces very frequently parallel to the 

 edges of combination between Pr and P. 



Lustre imperfect metallic. Colour intermediate be- 

 tween iron-black and dark greyish-black, passing 

 into greenish-black. Streak black, sometimes in- 

 clining to green or brown. Opake. 



Brittle. Hardness = 5-5 ... 6-0. Sp. Gr. = 3'994, 

 a crystalline variety from Elba. 



Compound Varieties. Massive : composition co- 

 lumnar, thin and straight, sometimes granular, the 

 individuals being scarcely distinguishable. 



OBSERVATIONS. 



1. According to DESCOTILS, the di-prispiatic Iron-ore 

 consists of 



