Count de Bournon o« the Laumonite. 87 



But on further examination I find this substance occurring in 

 specimens from various other places. 1 have in my possession a 

 specimen from the Island of Ferroe, in which pretty large crystals, 

 of a dull white aspect, and almost pulverulent, but of which the 

 figure is still perfectly discernable, are grouped with stilbite in larger 

 crystals, and not in the least altered, on a layer of quartz about three 

 lines thick, enclosing a nucleus of that sort of argillaceous and earthy 

 rock, well known as the gangue of the zeolites of Ferroe, and from 

 which it is separated by a thin layer of green ferruginous earth. 

 The exterior surface of this quartzose layer, on which the crystals 

 of laumonite are placed, is covered by a vast quantity of small crys- 

 tals of stilbite, differing in figure from those of the same substance 

 that accompany the laumonite, the forms of both of which belong 

 to the very numerous series of crystals of this substance, that have 

 not yet been described. 



I have another small group of laumonite also from Ferroe, the 

 crystals of which, unmixed with any other substance, are placed on 

 a small layer of granular quartz of a loose texture, the grains of 



of the rock from the portions of it remaining attached to the pieces which I have exa- 

 mined, the walls of the vein, to which this substance, with the carbonate of lime which 

 accompanies it, adheres, consist of a ferruginous argillaceous schist of a deep blackish- 

 grey colour, of a very loose texture, and traversed by small veins of carbonate of lime. 

 A moderate action of the fire changes this colour to a reddish-brown, and at the same 

 time renders this schist extremely attractable by the magnet ; its texture likewise becomes 

 more loose, and when examined with a glass and by the light of the sun, this substance 

 appears to be formed of a mass of small and extremely thin scales : its aspect is then much 

 like that Avhich wonld be presented by a mass of chlorite of the same colour, and of a fine 

 grain. I am indebted to M. Gillet de Laumont for another very fine specimen of this 

 mineral which I have received since that mentioned in the first part of this paper, in m hich 

 the crystals of laumonite are very large and regular and beautifully grouped with crystals 

 of carbonate of lime. The base of this specimen bears very evident marks of its having 

 been detached from the schist wliich I have just described. 



