V. Memoir on the Laumonite. 



By M. Le Comte de Bournon, F.R. & L.S. &c. 



Foreign Secretary of the Geological Society. 



[Translated from the original French Manuscript.] 



1 HIS substance, which has been long known under the name of 

 efflorescent zeolite, has been termed Laumonite by Werner, in honour 

 of M. Gillet de Laumont, to whom we are indebted for our first 

 knowledge of it, as well as for many other important contribution* 

 to the science of mineralogy. 



The former name of this mineral (efflorescent zeolite) was given to 

 it, in consequence of the property it has of not being able to bear, 

 even for a short period, exposure to the air without undergoing dis- 

 integration and finally falling into powder ; and the opinion most 

 generally entertained with respect to it was, that it belonged to the 

 species of mesotype. It is however altogether different from that 

 substance, nor does it belong to any of the numerous series of zeo- 

 litic minerals, which have hitherto been made known to us. 



Highly calculated however as this substance is to excite the inte- 

 rest and the curiosity of the mineralogist, we have as yet had but 

 very slight and imperfect descriptions of it. The author who has 

 spoken of it most in detail is the Abbe Haliy. 



