OIIDERX. PRISMATIC I RON- 1'Y KITES. 4G3 



streaked in a vertical direction, though smooth. 

 The remaining faces smooth. 



Lustre metallic. Colour pale bronze-yellow, some- 

 times inclining to green or grey. Streak, grey- 

 ish-black or brownish-black. 



Brittle. Hardness = 6-0 . . . 6-5. Sp. Gr. = 4-678, 

 crystals from Schemnitz ; 4-847, crystals from 

 Littmitz. 



Compound Varieties* Twin-crystals: 1. Face of 

 composition parallel, axis of revolution perpendicu- 

 lar to a face of Pr ; 2. Face of composition paral- 

 lel, axis of revolution perpendicular to a face of Pr. 

 The first law of regular composition occurs very 

 frequently in the present species, and is often re- 

 peated either in parallel layers, or in the directions 

 of both faces of the prism at once. Thus in Fig. 

 42., two individuals, P l and P 11 are attached to the 

 individual P, and in a similar manner the composi- 

 tion is continued in the individuals P 111 andP IV ; 

 the whole group, consisting of five individuals, has 

 very much the appearance of a five-sided pyramid 

 with truncated apices, each of the five solid angles 

 at the base shewing a re-entering angle. The se- 

 cond law generally takes place in such varieties as 

 are already compound according to the first. They 

 assume a grooved appearance like Fig. 43. The 

 re-entering angle, formed by the faces r + oo (P 

 and P", or P 1 and P 1 ") is = 114 lO'. Globular, 

 reniform, stalactitic and other imitative shapes : sur- 

 face drusy ; composition columnar, individuals 



