122 



Manganite, the Monohydrated Manganese Oxide, which is 

 isomorphous with Goethite, has already been mentioned as occurring 

 at Force Crag Mine, near Keswick, in association with Smaltine, 

 Tourmaline, Stoltzite, Cerussite, Blende, and many other minerals. 

 It will probably be detected when properly looked for also in the 

 Roughten Gill Mines, especially around Dry Gill ; but I have not 

 yet seen a specimen from our district myself. 



The commonest ore of Manganese, at least in the Caldbeck 

 Fells, is the amorphous. Hydrous Peroxide of Manganese, known 

 as PsiLOMELANE. This occurs in considerable abundance at Dry 

 Gill Mine, where the barrel-shaped crystals of Mimetesite or 

 Kampylite are found. Beautiful specimens of both of these are in 

 the British Museum, the Museum of Practical Geology, the Hark- 

 ness Collection, and others. 



This, like Pyrolusite, is a valuable ore of Manganese, but, unless 

 it occurs in large quantities, it hardly pays for working at places 

 where transport is costly. 



The most important rock-constituent in our district is, without 

 doubt, one form or another of the mineral Quartz. As the mode 

 of occurrence of this mineral in the Lake District has already been 

 treated of by Mr. Ward in Vol. iii. of our Transactions and else 

 where, it would be out of place for me to repeat any of his 

 observations here. The mineral, in one form or another, is to be 

 found almost everywhere ; but in the form of veins it is found but 

 rarely in the Carboniferous Rocks, and hardly ever in any of the 

 newer rocks of our district, There is abundant proof that this is 

 owing to the fact that most of the quartz veins traversing the older 

 rocks of the Lake District are of older date than the Carboniferous 

 period. Veins of quartz of Carboniferous age do, however, occur, 

 and there is this of interest about many of these Carboniferous 

 quartz veins — that they afford remarkable instances of a kind of 

 replacement, similar in its nature to that of the Haematite, the 

 Dolomite, and one or two other minerals already referred to. One 

 instance of this kind, well known by name, is that of the Great 

 Sulphur Vein of the Alston district. This has already been 



