187 



Green Slates so largely quarried at Patterdale, and again near 

 Ambleside, and so much used for roofing purposes even in Penrith 

 and the neighbourhood, owe their peculiar glaucous tint to the 

 abundant presence of this mineral. Mr. Ward has treated of the 

 mode of occurrence of Chlorite in these rocks in considerable 

 detail in a paper printed in the Mineralogical Magazine^ No. 4, 

 (1877). The general conclusion he arrived at is that Chlorite 

 represents a decomposition-product of several other minerals ; and 

 that, under conditions of extreme metamorphism, it may again be 

 converted into one or another of the anhydrous crystalline 

 silicates. The Chlorite group here has not yet been fully studied. 



GiLBERTiTE, one of the hydrated forms of mica, occurs com- 

 monly in connection with the granite of the Cawda, near the 

 well-known lead mines. 



Another hydrated silicate is represented by Vermiculite. This 

 mineral was first recognized as occurring in Cumberland, I believe, 

 by Professor John Morris, F.R.S., who shewed that much of the 

 crystalline matter occurring in the Eskdale and Bootle Granite 

 previously regarded as mica, was really Vermiculite. Probably a 

 careful search would prove its existence in other localities as well. 



Tourmaline, Boro-silicate, or its variety Schorl, occurs in 

 the form of divergent groups of glossy dark-brown acicular crystals 

 in the plutonic rocks of the Carrick Fell area. One or two fine 

 specimens collected from this locality are now in the Mineral 

 Collection at the Carlisle Museum. Schorl has also been recognized 

 by Mr. Wilfrid Huddlestone, and by Mr. William Atkinson, of 

 Knock, in the form of small radial groups of acicular crystals, 

 which occur along divisional planes of the Quartz-felsite now so 

 extensively-quarried by the Cumberland Road-Metal Company at 

 Threlkeld. It is also met with in small nests and veins in some 

 of the metamorphosed tuffs of Bala age that occur in the neigh- 

 bourhood of the Shap Granite. Other localities are Tentergill, 

 Braithwaite, and Skidda Foot. 



Amongst the Silico-tantalates, Sphene, as a native mineral, has 

 some claim to mention here. It is most commonly met with in 

 the boulders of Criffel or Dalbeattie Granite, so plentifully distri- 



