ORDER V. RHOMBOHEDRAL GRAPHITE-MICA. 101 



original repositories, but like the white powder of the 

 crystals, they soon assume a blue tinge, on being exposed 

 to the air. 



3. The varieties of the present species occur in different 

 kinds of natural repositories. Some of them are found 

 crystallised, particularly accompanied by hexahedral Iron- 

 pyrites in copper and tin veins ; others in very narrow veins 

 traversing greywacke, partly with hexahedral Gold, and 

 other species, which accompany the latter; still others, 

 probably in beds, along with rhombohedral Iron-pyrites, 

 octahedral Iron-ore, and some at last are disseminated in 

 basalt, and other trap rocks. The compound, friable varie- 

 ties are imbedded in clay, and in the depositions of bog 

 iron-ore, which indicate a more recent formation of it. 



4. The first varieties exhibited in the cabinets of mi- 

 nerals were those from Vorospatak in Transylvania, where 

 they are found in the gold mines, and have been consider- 

 ed as blue gypsum. The Vivianite occurs near St Agnes 

 in Cornwall, the Prismatic Blue Iron at Bodenmais in 

 Bavaria, in several districts of France, in Isle de France, 

 &c. partly imbedded in mountain rocks. The Earthy Blue 

 Iron is found in the Gail valley in Carinthia, at Ligist and 

 other places in Stiria, at Eckartsberge in Thuringia, in 

 Wurtemberg and Baden, in Lusatia, and other countries. 

 It has been discovered in several peat mosses in the Shet- 

 land Islands, also at Ballagh in the Isle of Man, where it 

 is associated with elks' horns, in river mud near Liver- 

 pool, &c. 



GENUS IV. GRAPHITE-MICA. 

 1. RHOMBOHEDRAL GRAPHITE-MICA. 



Rhomboidal Graphite. JAM. Syst. Vol. II. p. 216. Man. 

 p. 117. Plumbago. Graphite. Black Lead. PHILL, 

 > 364. Graphit. WERN. Hoffm. H. B. III. 1. S. 

 309. Graphit. HAUSM. I. S. 67. Graphit. LEONH. 

 S. 334. Fer carbure'. HAUY. Traite', T. IV. p. 98. 

 Graphite. Tabl. comp. p. 70. Fer carbure ou Gra* 

 phite. Traite', 2de Ed. T. IV. p. JJa. 



