Magnesite of the Paris Basin, Sfc. S85 



k is as productive as the first in general results, and conse- 

 quently as proper as it to discover the laws whfch have pre* 

 sided at the structure of the earth, and at the formation of 

 the minerals that enter into its composition. 

 - It is under this last point of view that I shall consider the 

 mineral which I have mentioned by the name Magnesite. 



The following are the minerals to which I give this name. 

 I distinguish them in two principal series, which may one 

 day be separated into two species when we shall have ob- 

 served sufficiently essential characters to establish this dis- 

 tinction. 



1. Plastic magnesite (magnesite plastique), composed of 

 tnagnesia, silex, and water, without carbonic acid. 



I here comprise the magnesite, so improperly named ecume 

 de Mer, that of the environs of Madrid, that of the environs 

 of Paris, that of Salinelle, department of the Gard, &c. 



Serpentine might, from its composition, almost be referred 

 to this species ; but it is distinguished from it by its mine* 

 ralogical characters. 



2., Effervescent magnesite (magnesite efFervescente), es- 

 sentially composed of magnesia and carbonic acid, sometimes 

 associated with very variable proportions of silex and water. 



We may refer to this division the magnesite of Hroub- 

 schitz in Moravia: those of Piedmont, ef the Isle of Elba, 

 of Baumgarten in Silesia, of Styria, &c. 



Having made known, as far as it appears necessary, the 

 minerals I include under this name, I shall now describe the 

 position of the magnesite of the Paris basin, and present the 

 union of a few facts and observations in order to complete 

 the geognostic history of these minerals, the principal object 

 of this notice. 



Parisian Magnesite. 



I first observed the presence of magnesite in rather extenr 

 sive beds at Coulommiers, twelve leagues to the E. of Paris, 

 and afterwards quite close to the latter town : I shall des- 

 cribe this variety and the circumstances of its position witl^ 



