68 MINERAL RICHES OF OUR VICINITY. 



vidual of high reputation : but the persevering labours 

 of our townsman, the Rev. R. Hennah, Chaplain of 

 the Citadel, have not only established the fact of their 

 existing and abounding here, but collected a very ex- 

 tensive assemblage of them, some of which do not 

 appear hitherto to have been found elsewhere. The 

 produce of the lime quarries is the more particularly 

 described, from their convenient proximity, to the 

 student. 



2. Next to the limestone we have named Serpen- 

 tine. Something resembling this seems to exist near 

 Horrabridge, though it has not been yet enough exa- 

 mined to name it positively. At Mr. Trelawny's es- 

 tate of Colrinick (or near it), is Clicker Tor, undoubt- 

 edly a variety of Serpentine. In both these are found 

 Tremolite and Asbestos, and probably Actynolite, Steat- 

 ite and Magnesite. Bronzite is also frequently found 

 in serpentine, and if not in those particular ranges of 

 it, may nevertheless be obtained in our neighbourhood ; 

 for in the " sand pit," on the Saltash Road, near Mount 

 Tamar, a variety of Bronzite, in a micaceous form, 

 seems to constitute pretty nearly half of the rock. No 

 Serpentine, however, appears to exist in its immediate 

 neighbourhood . The above enumerated are but a small 

 portion of the minerals found in Serpentine ; but until 

 our rocks of that character have been more examined, 

 \ve must not give them credit for subjects which they 

 may not be found to possess. 



3. Porphyry is a fertile mineralogical reservoir; 

 and of Porphyry itself we have considerable variety. 

 On the south side of Mt. Edgecumbe, running into 

 Cawsand Bay, we have a Porphyry of little sparkling 

 crystals, apparently of Felspar, imbedded in a sub- 

 stance closely resembling red Sandstone. Running 

 through the Slate, as it approaches the Granite, toward 

 Shaugh and Dartmoor, \ve have veins of Porphyry, of 

 miles in length, composed chiefly of compact Felspar ; 

 and imbedding rare but occasional crystals of pyrites 

 and transparent felspar. Grenofen Hill, and that on 

 which Walkhampton Church is built, are porphyry, 



