OXDEttXI. IIEXAIIEDRAL LEAD-GLANCE. 15 



Common and Compact Lead-glance, according to the crystallised 

 state of the individuals, or the size of the grain in the com- 

 positions. By decomposition sometimes a black sooty sub- 

 stance is produced, called Friable Lead-glance. 



2. According to THOMSON, the hexahedral Lead-glance 

 consists of 



Lead 85-13. 



Sulphur 13-02. 



Iron 0-50. 



It is Pb S a , the proportions of lead and sulphur being 

 = 86-55 : 13-45. Some varieties contain a small quantity 

 of silver, others antimony. Before the blowpipe it melts, 

 if it is heated with precaution, and yields globules of me- 

 tallic lead, after the sulphur has been driven off. It is partly 

 soluble in nitric acid, and leaves a white residue. 



3. Hexahedral Lead-glance is frequently found in veins, 

 but also in great quantity in beds, particularly in limestone 

 rocks. In beds it is accompanied by various other ores of 

 lead, also by dodecahedral Garnet-blende, several species 

 of Pyrites, Iron-ore, &c. ; in veins it occurs, besides these, 

 along with ores of silver, copper, and antimony, sometimes 

 with hexahedral Gold. In both kinds of repositories it is 

 associated with octahedral Fluor -haloide, rhombohedral 

 Lime-haloide, rhombohedral Quartz, and many other spe- 

 cies. 



4. The remarkable beds of hexahedral Lead-glance in. 

 Carinthia, which occur in limestone, and are worked at 

 Deutsch-Bleiberg, Windisch-Bleiberg, Windisch-Kappel, 

 Ebriach, and other places, possess in several respects a 

 striking similarity to those of Derbyshire, Durham, and 

 Northumberland, in England, in both of which countries 

 they are accompanied and intersected by lead veins. But it 

 is also found in beds in older rocks, as in Stiria, Carinthia, 

 &c. In veins it occurs in rocks of various ages, from gneiss 

 to the coal formations, in several parts- of Saxony and Bo- 

 hemia, in the Hartz, in Anhalt, in Hungary y in Transyl- 

 vania, in France, in Scotland, and in many other countries. 



