ORDER Vlii. PRISMATIC IKON-ORE. 413 



2. According to D'AuBuissoN, the present species con- 

 sists of 



Peroxide of Iron 82-00 84-00. 



Water 14-00 11-00. 



Oxide of Manganese 2-00 2-00. 



Silica 1-00 2-00. 



It is a hydrate of peroxide of iron, 2 Fe 4- 3 Aq, the pro- 

 portions of peroxide of iron and water being as 85 30 to 

 14-70. The first analysis refers to a hematitic variety, and 

 the second to a compact one. Before the blowpipe it be- 

 comes black and magnetic. It melts with borax into a 

 green or yellow glass, and is soluble in heated nitro-muria- 

 tic acid. 



3. The present species occurs in beds and veins. In the 

 first it is very generally accompanied by brachytypous Fa- 

 rachrose-baryte, sometimes also by prismatic Hal-baryte, 

 rhombohedral and prismatic Lime-haloide, rhombohedral 

 Quartz (often Calcedony), and other species. These beds 

 are included both in ancient and in secondary rocks, the 

 latter of which, though very thick, do not extend to a great 

 distance. It is frequently associated with the species of the 

 following genus, particularly where it occurs in veins. In 

 these repositories also a crystallised variety in thin lamellae 

 has been found, and has received the name of Rubinglimmcr 

 or Gothite. Another variety in velvety reniform shapes oc- 

 curs in silver-veins, with hexahedral Lead-glance, &c. 

 Acicular crystals are met with in geodes of rhombohedral 

 Quartz, probably formed in veins, and in agate balls. Those 

 varieties of clay iron-stone which belong to the present 

 species either form beds by themselves in secondary rocks, 

 or they are imbedded in strata of clay in the shape of lar- 

 ger or smaller globular concretions, some of them belonging 

 to the coal measures, others to various kinds of sandstone. 



4. Prismatic Iron-ore is very plentiful in some countries. 

 It is found in beds in gneiss along with granular limestone, 

 at Friesach, at Hiittenberg, and in the valley of Lavant in 

 Carinthia, at Turrach and Eisenerz in Stiria ; in the last 



