190 



the Great Exhibition of 185 1. It is now located in the Museum 

 of Practical Geology. It weighs over a hundredweight. Ver)r 

 fine crystals from the mines of the same district are in the British 

 Museum Collection. Beautiful sapphire-blue, pale milk-blue, or 

 lead-blue crystals, and occasionally others of a clear rose-colour, 

 are obtained from the West Cumberland hematite mines, 

 especially from Hinniside and Frizington. Considerable variety 

 occurs in the form of crystals obtained from different local- 

 ities ; and crystals of particular form, or of particular modes 

 of occurrence, are so characteristic of particular localities, that 

 practised mineralogists that have many specimens passing through 

 their hands can often name unerringly the precise locality whence 

 a particular specimen under notice may have been derived. A 

 careful investigation of these facts might throw considerable light 

 upon many points, connected with the genesis of minerals, at 

 present imperfectly-understood. I have myself noted many ; but 

 it is impossible to describe them without entering fully into 

 crystallographic details ; which would be a little out of place in 

 such papers as the present. 



Mention has already been made* of the entire removal of large 

 crystals of Barytes from the interior of investing masses of crystals 

 of Calcite at Dufton. A specimen illustrating this is exhibited in 

 the Mineral Collection at Carlisle Museum. 



Judging by its mode of occurrence, Barytes is, in many cases, 

 one of the oldest vein-minerals, after quartz, that is found in the 

 district. Some of it is older than part of the quartz associated 

 with it, because pseudomorphs of Barytes in quartz are not un- 

 common ; especially in the vein-contents of the Caldbeck Fells. 

 Haematite, too, often replaces Barytes, and helps to prove their 

 relative ages in these particular cases. The British Museum 

 collection contains pseudomorphs of Barytes after Barytocalcite, 

 from Alston, and of Calamine after Barytes, from Rowtin Gill. 



Anglesite, Lead Sulphate, occurs in bright, vitreous, translucent 

 crystals, usually of no great size, in the vein-stuff traversing the 

 Caldbeck Fells. The largest crystals are obtained from Rowtin 

 * Transactions of Cumb. and West. Assoc. No. VIII., p. 196. 



