302 Dr. Bonsdor on Tabular Spar from Pargas. [Oct. 



The analysis, consequently, gives as the constituents of the 

 tabular spar : 



Silica 52*58 containing 26*45 of oxygen 



Lime 44*45 12*49 . 



Magnesia 0*68 0*26 



Protoxide of iron. 1*13 0*26 



Alumina Trace 



Volatile matter . . 0*99 



99*83 



It is to be observed that the small portions of magnesia and 

 oxide of irort^aa only be considered as mechanically mixed, but 

 even in this state they must be combined with a portion of silica, 

 and very probably they form a bisiliciate ; then 0*26 + 0*26 = 

 052 and 0*52 x 2 = 1*04 ; consequently, this quantity of oxy- 

 gen, when subtracted from the oxygen of the silica, will leave it 

 25*41 ; and when we double the oxygen of the lime, we shall 

 have 24*98, which is very nearly equal to the quantity of oxygen 

 in the silica; and it may be further observed, that the quantity 

 of silica is probably increased by the imperfect separation of the 

 small grains of quartz : this mineral is, consequently, a bisiliciate 

 of lime, and its mineralogical formula as C S*. 



It is stated by Klaproth, who first analyzed the tabular spar, 

 that this mineral from Dognatzka, in the Bannat, besides 50 per 

 cent, of silica, contained 5 per cent, of water. On this account, 

 I have endeavoured, as much as possible, to ascertain the true 

 quantity of volatile matter; but the results of our experiments 

 indicate great difference in this respect. It is, however, known, 

 "from the examination which M. Berzelius has made of this mine- 

 ral from the Bannat with the blowpipe, that it contains no water 

 at all, and, consequently, the difference of composition which 

 appears to exist in the minerals is explained. 



As it is proved that the tremolite from Pargas agrees perfectly 

 in composition with the tabular spar, it may be concluded that 

 thelatter has been frequently mistaken for the former. At the 

 village of Perhonjemi, in the government of Kymmene, in Fin- 

 land, there occurs a fine white radiated mineral, which has been 

 considered to be tremolite, but a recent analysis of it by M. Hose 

 gives 51*60 silica and 46*41 lime, with I'll of actinote mecha- 

 nically intermixed. At Gokum, near Danemora, in Sweden, a 

 mineral is found, which very much resembles the tabular spar 

 from Pargas, and which has been found to be similar also in 

 composition. 



