OHDEK xi. DI-PRISMATLC COPPER-GLANCE. 7 



Compound Varieties. Twin-crystals: axis of re- 

 volution perpendicular, face of composition parallel 

 to a face of the horizontal prism fr. The indivi- 

 duals are generally continued beyond the face of 

 composition. The axes of two individuals cross 

 each other at angles of 93 4W and 86 2&. The 

 composition is frequently repeated in parallel layers, 

 and forms striae upon the faces, particularly upon 

 the pyramid P, and upon the prism f r itself, but 

 also upon those which produce with it parallel edges 

 of combination. The situation of these striae is 

 useful for discovering the true position of the faces 

 of pyramids and prisms. Massive : composition 

 granular, strongly connected. 



OBSERVATIONS. 



1. Two varieties, one from Cornwall, and another from 

 Claustlial, have yielded to KLAPROTH, 



Antimony 25-50 19*75. 



Lead 39-00 42-50. 



Copper 13-50 11-75. 



Iron 1-00 5-00. 



Sulphur 16-00 18-00. 



Before the blowpipe upon charcoal it melts, smokes, and 

 yields afterwards a black globule. In a strong heat the 

 charcoal becomes covered with oxide of lead. It is easily 

 soluble in heated nitric acid. 



2. Di-prismatic Copper-glance has been hitherto found 

 only in veins, and is accompanied by axotomous and pris- 

 matoidal Antimony -glance, hexahedral Lead-glance, dode- 

 cahedral Garnet-blende, &c. 



3. The first varieties of this species noticed by mineralo- 

 gists were those from Cornwall, where they occur with 

 axotomous Antimony-glance hi Wheal Boys in the pa- 

 rish of Endellion near Redruth. Another variety, from 



