Northumberland and Durham. 85 



Ores of Iron. 

 Iron Pyrites. — Massive and Crystallized. 



Carbonate of Iron. — Pearlspar; massive, mammellated, and in small 

 lenticular crystals, yellowish white, light and dark brown, 

 and black from decomposition ; too common in all the 

 mines. 



Ores of Zinc. 

 Blende. — Black and brown, amorphous and crystallized ; in all the 

 mines. 

 Reddish brown, in small crystals, scattered over quartz and 

 fluor spar, and in minute crystals upon stalactitical brown 

 quartz ; from Aldstone moor. 

 Blood-red irregular crystals on limestone, with crystals of 

 purple fluor ; from Aldstone moor. 

 Calamine is worked in old Hagg's cross vein near Nent head. One 

 variety is of a yellowish grey colour ; conchoidal in 

 fracture, and in a slight degree transparent : another is 

 snow white and perfectly opake. 

 Ore of Zinc. — In thin white opake layers or incrustations from 

 Allenheads. 



Salts of Lime. 

 Carbonate of Lime. Calcareous Spar. — In acute and obtuse pyramids, 

 (the dog tooth and nail head spar) from Aldstone moor. 

 In dodecahedrons on pearl spar i^Sowerby, t. 42) from Ald- 

 stone. 

 In 6-sided highly transparent prisms terminated by 6-sided 

 pyramids, called Tyne bottom spar ; from the Tyne 

 bottom limestone on Aldstone moor. 

 In pale straw coloured 3-sided pyramids. This delicate 

 fossil has been observed in a vein opposite New-house 

 in Weardale. 



