74 Dr. Blum on Pseudomorphous Minerals. 



At Gopfersgriin the gangue is a steatitic slate, lying between 

 mica slate below, and probably granular limestone or Dolomite 

 above ; and there is every reason to believe that the steatitic 

 rock is an altered mica slate. After passing through twenty four 

 to thirty feet of the decomposed slate of the surface, the steatite 

 first appears, and continues for fifty or sixty feet : below this the 

 pseudomorphous quartz and bitter spar are obtained both in crys- 

 tals and massive. Near by this, the mica slate becomes penetra- 

 ted with granular limestone. At Hohlenbrunn the same granu- 

 lar limestone contains, besides masses of quartz, octahedrons of 

 fluor spar. These facts are urged by Dr. Blum as evidence that 

 the same process which produced the steatitic pseudomorphs, 

 changed the rock containing them from a mica slate. The stea- 

 tite replacing the quartz is quite pure, while that of the slate is 

 brown and impure from the iron in the mica, and looks like a 

 clay slate. 



The serpentine of Monte Rosa affords similar pseudomorphs. 

 Dr. Blum describes a geode in his collection in which the ter- 

 minal angles are steatite, and the exterior of the crystals has 

 become yellowish-white or brownish-red, without affecting the 

 sharpness of the edges or smoothness of the surfaces. The spe- 

 cimen is from Olmutschen in BTahren. 



Similar crystals have been found by Prof. Emmons in the ser- 

 pentine of Middlefield, Mass., and by Dr. Fowler in the granular 

 limestone of Newton, N. J. 



Pimelite is supposed by Dr. Blum to have often originated by 

 similar changes, and also meerschaum in many instances. No- 

 dules of meerschaum at Hrubschnitz, in serpentine, have often 

 he states a nucleus of Jii'estone, (a coarse kind of opal, occurring 

 there in similarly shaped nodules,) while others are wholly meer- 

 schaum. Dr. Blum suggests that the silica that has passed off 

 in the change is found in the opal that occurs at the same 

 locality, and finds proof of this in the forms and position of the 

 opal. 



Steatite with the form of Andalusite. — Pseudomorphs of this 

 kind have been described by von Leonhard and Goldfnss and 

 Bishof The change is a simple replacement of the alumina by 

 magnesia. 



Steatite with the form of Topaz. — The gneiss of Ehrenfrie- 

 dersdorff, including with the tin ore and quartz, talc, lithomarge, 



