Mr. ConnePs Analysis of Levyne. 43 



For the purpose of comparing this analysis with the con- 

 stitution of chabasite, we may take the following examples of 

 the analysis of the ordinary lime chabasites. 



Silica 50-65 ... 48*38 ... 50*14 



Alumina 17*90 ... 19*28 ... 17*48 



Lime 9*73 ... 8*70 ... 8*47 



Potash 1*70 ... 2*50 ... 2*58 



Water 1950 ... 20*00 ... 20*83 



99*48* 98*86 f 99*50$ 



From this comparison it undoubtedly appears that the mi- 

 neral under examination possesses, chemically speaking, con- 

 siderable analogy with chabasite, but still the differences seem 

 to be such as prepare us for admitting it as a distinct species, 

 provided that its crystallographical and optical properties lead 

 us to that conclusion. 



Had the form of the crystal of levyne been found to be the 

 same as that of chabasite, we might have admitted that the 

 differences of the composition of the two minerals arose from 

 accidental impurities, examples of such discrepancies some- 

 times occurring in regard to different individuals of the same 

 species, as in the different analyses of barytic harmotome. But 

 according to the determination of Mr. Haidinger, the crystal- 

 lographical differences between levyne and chabasite are of a 

 very marked description, the fundamental form of the former 

 mineral being a rhomb of 79° 29', whilst that of the latter is a 

 rhomb of 94° 46'. A like discrepancy occurs in regard to the 

 optical properties as determined by Sir David Brewster, levyne 

 conforming to the general law of rhombohedral crystals in 

 having one axis of double refraction, whilst the optical struc- 

 ture of chabasite is very anomalous. 



It would appear, therefore, that we cannot hold chabasite 

 and levyne to be the same mineral without disregarding cry- 

 stallographical and optical differences of a marked description ; 

 and on the other hand, there evidently appear to be sufficient 

 chemical differences to entitle us to give effect to the distinc- 

 tions of external and optical characters, the difference of com- 

 position being at least as great as that between some other 

 well established species, as, for instance, between stilbite and 



* From Gustavsberg, analysed by Berzelius. — Edinb. Phil. Journal, 

 vol. vii. p. 10. 



t From Fassa, analysed by Arfwedson. — Ibid. 



X From Renfrewshire, analysed by myself. — New Edinb. Phil. Journal, 

 ▼ol. vi. p. 26C. 



G2 



