MINERALOGY. 121 



of them, when more nicely- examined, may per- 

 haps be found to belong to the fame order, and 

 perhaps be fome kind of earth, whofe properties 

 have been long and perfectly known. 



The terra porcellanea Luneburgica, which Bruck- 

 man mentions, and Mr. Wallerius has ranked 

 among the gypfa, may, perhaps, belong to this 

 order : but I have not been able to procure a fpe- 

 cimen of it, to compare it with the zeolites, 

 which alfo is very fcarce, not being found in our 

 country except in very fmall veins and cavities. 

 To this fcarcity is owing, that it has not yet been 

 tried in the fire together with other kinds, except 

 with the fparry fiuor. With that it does not fufe 

 very readily, becaufe, when equal parts of them 

 are melted together, an opaque flag or glafs is 

 produced of the fame colour with the alcali of 

 nitre, of a fibrous texture, and of an uneven fur- 

 face. 



The quality of fwelling in the fire, like the 

 borax, is peculiar to the criflals, (Se£t. cxi.) be- 

 caufe the other varieties rife only into fome fmall 

 blifters, which are of a white colour at their 

 edges, and inftantly cover themfelves with a white 

 glaffy fkin, after which they become quite refrac- 

 tory. 



SECT. CXIII. 



The Ninth Order, 



The Manganefe Kind, Magriejia* 



The ftones belonging to this order, are in 

 Swedifh called Brunften, in Latin Sydere*, 

 or Magnefia nigra, in order to diflinguifh 

 them from the Magntfia alba officinalis, and 

 in French Mangonefe, &c. They are by fome 



litho- 



