56 



is said to be owing to their containing more silver. Some 

 varieties have a diverging striated fracture. This ore 

 holds lead in the metallic state. Before the ,blowpipe on 

 charcoal it decrepitates, but melts easily with a sulphureous 

 smell, part sinking into the charcoal. If alternately heated 

 and cooled, it will at last vanish, and leave its silver, if it 

 contains any. Berg. 493. — Spec. grav. 7^587. Brisson. 



