1873.] OOl [Gentll. 



ticular attention to that which occurs between Media, Delaware County, 

 Pennsylvania, and the Asylum for Feeble- Minded Persons. On a fresh 

 fracture, the silky lustre of its fibres can be easily perceived, but it has 

 a slaty structure and is associated with white and pale blueish crystals 

 of cyanite and brown staurolite crystals, many of them in twins. The 

 whole reminds one immediately of the well known staurolite and cyanite 

 crystals in the paragonite slate of St. Gothard. 



A similar fibrolite slate is found near the Culsagee Mine, Macon 

 County, North Carolina. 



Amongst fifty crystals of corundum from Laurens District, South 

 Carolina, part of which are converted into damourite, I found one 

 broken crystal, the outside of which is changed into fibrolite. It is an ir- 

 regular six-sided prism, § of an inch long, not quite half an inch thick, 

 with a core of unaltered brownish corundum \ of an inch in diameter. 

 The fibrolite is radiating from the surface towards the core, and the 

 surface is covered with crystalline aggregates of fibrous fibrolite and a 

 few small plates of damourite. 



For a highly interesting specimen, I am indebted to John C. Traut- 

 wine, Esq. He found it many years ago at Germantown, Pennsylvania. 

 It consists of granular quartz with streaks of grayish-white fibrous fibro- 

 lite through it from ± to § of an inch in width, but less than a line in 

 thickness. The centre of several of these streaks is occupied by blue 

 bladed cyanite. It is impossible to decide, whether this is a case of 

 paramorphism, in which the monoclinic changes into the triclinic silicate 

 of alumina, A1 2 ; „ SiO., or whether both crystallized from the same 

 medium in their present form. 



13. Cyanite. 



Cyanite is a very usual associate of corundum. It is found with it on 

 the St. Gothard, near Petschau in Bohemia, and in several other foreign 

 localities. It is one of the most important results of its alteration. I 

 have dwelled at fuller length upon the change of corundum into fibrolite, 

 because there we have real pseudomorphs which appear not to exist with, 

 chemically, the same aluminous silicate, the bladed structure of the 

 cyanite immediately obliterating, probably, every trace of the original 

 form. However, I shall describe a number of specimens of cyanite, 

 containing still a nucleus of the original mineral, from which they 

 resulted. 



a. At Litchfield and Washington, Connecticut, rolled masses of cyanite 

 have been found, which contained corundum and diaspore. I am in- 

 debted to Prof. Geo. J. Brush, for a very beautiful and instructive speci- 

 men from Newton, Connecticut. It consists of irregularly arranged 

 bladed masses of gray and blueish-white and blue color. In some 

 places, and especially, where the blades meet, a white or yellowish-white 

 micaceous mineral is intermixed ; imbedded in it sometimes is diaspore> 

 and in one place in immediate contact with the cyanite, is a rounded 

 fragment of a slightly pink colored corundum. 



