282 DESCRIPTION OF THE MUSEUM. 



we observe the inverse quartziferous variety, 

 commonly called crystallized sandstone of Fon- 

 tainebleau; but which in reality is only carbo- 

 nate of lime mixt with sandy particles. Its crys- 

 tals frequently form groups of considerable size, 

 such as those we see on the shelves of the same 

 case. 



The bituminiferous carbonate of lime consti- 

 tutes the black marbles of Dinant and Namur, and 

 is employed for paving churches. 



In the sixth case we have another species, called 

 arragonite, of which there is at the bottom a 

 considerable block, given by M. Lacoste de Plai- 

 sance, professor at Clermont-Ferrand. The most 

 remarkable of its varieties is the coralloid, for- 

 merly known under the improper denomination 

 of Jlos ferri, which frequently rivals snow in 

 whiteness : it is a stalactite, the twisted branches 

 of which are entwined together. Here are very 

 fine groups of it from Eisenerz, in Styria. 



The third species is the phosphate of lime. In 

 the seventh case we observe the earthy variety 

 from Estramadura, where it is employed in 

 building. Its dust, when thrown upon red-hot 

 charcoal, emits a beautiful phosphoric light. 



In the eighth case is ihejluate of 'lime ; a sub- 

 stance known in the arts under the name ofjluor- 

 spar, remarkable for the diversity of the colours 



