256 Prof. J. P. Cooke on the Vermulites. 



Professor J. Lawrence Smith, in his recent article in Amer. 

 Journ. Sci. (III.) vol. vi. p. 180, says that "in the development 

 in North Carolina the corundum " (with which the vermiculite 

 is associated) " occurs in chrysolite or serpentine rocks, and out- 

 side of serpentine it has not been found. These chrysolite rocks 

 belong to a regular system of dikes which have been traversed 

 for the distance of about one hundred and ninety miles. This 

 system of dikes lies on the north-west side of the Blue Ridge, 

 and has a strike parallel to the main mass of the ridge, and has 

 an average distance from the summit of the ridge of about ten 

 miles. The serpentine appears at intervals along this whole 

 line of one hundred and ninety miles/' and " is usually enclosed 

 in a hard crystalline gneiss." In the serpentine the corundum 

 has been found at several localities along a distance of forty 

 miles. Colonel Jenks writes me : — " The workmen have opened 

 a new vein they call the gem vein. It is walled with chrysolite ; 

 and the fissure is from one to four feet wide, which fissure is 

 filled with ripidolite ; and in this the corundum crystals are im- 

 bedded." As regards the association of the ripidolite and ver- 

 miculite, he also writes : — " They occur both alone and inter- 

 mingled, and also in layers, like the leaves of a book." Again, 

 "The ripidolite maintains a uniform character of texture and 

 appearance, whether associated with the vermiculite or alone. 

 In the vein at the bottom of the shaft I have spoken of, and else- 

 where, it is of uniform hardness, texture, &c. ; but in it the co- 

 rundum seems to have lost cohesion — in some localities falling 

 to pieces, and crumbling out of the ripidolite matrix. But when 

 exposed to the air and sunshine for a day or two, the corundum 

 regains its cohesion, and you can then chip off the ripidolite 

 from it. It is just the opposite with the vermiculite when alone 

 the matrix. Sometimes it occurs in masses several feet long, 

 formed of scales as large as your hand, easily separating like 

 mica from the corundum, which in this matrix always seems to 

 retain its cohesion. Then, again, the vermiculite will occur in 

 masses of many bushels, all broken up and disintegrated, like 

 very coarse bran, in which the crystals of corundum lie like eggs 

 in a box of sawdust. The great crystal (weighing 316 pounds) 

 was thus deposited. At other places the entire mass seems to 

 have changed to the colour of white Castile soap, with specks of 

 green in it, the corundum crystals all falling apart until exposed, 

 when they harden." This un technical language of an unpro- 

 fessional but accurate observer conveys a very vivid idea of the 

 mode of association of these minerals. The specimens so kindly 

 sent me by Colonel Jenks confirmed in all respects his observa- 

 tions. In several cases the corundum was still imbedded in both 

 the ripidolite and the vermiculite ; and the scales of these minerals 



