304 On Sodalite. 
There are few minerals, however, that are so totally di- 
stinct in their external characters as the natrolite of Klap- 
roth, and the substance we are now treating of. The mi- 
neral examined by Klaproth occurs at Roegan*, on the 
Lake of Constance, in porphyry-slate, coating the sides of 
veins and cavities in a mamellated form, the texture of 
which is compact, fibrous, and radiated ; the colour pale 
yellow, in some places passing into white, and marked with 
brown zones. Hitherto it had never been found in a state 
sufficiently perfect to afford any indications of form. Lately, 
however, M. de Bournon was so fortunate as to procure 
some of it, presenting very delicate needle-form crystals, 
which, by means of a strong magnifier, he was able to as- 
certain presented flat rectangular prisms, terminated by 
planes, which, he thought, might form angles of 60° and 
120° with the sides of the prism. With this, neither our 
mineral nor the Swedish can have any connexion, further 
than some analogy which may exist in their composition, 
Concerning the Swedish mineral, I have not been able to 
ebtain much satisfactory information. There is a speci- 
men of it i: Mr. Allan’s cabinet, which he received di- 
rectly from Sweden, sent by a gentleman who had just be- 
fore been in London, and was well acquainted with the 
collections ef that city, from which it is mferred, that the 
specimen in question is the same as that examined by 
Count Bournon and Dr. Wollaston. 
Werner has lately admitted into his system a new mineral 
species, which he distinguishes by the name of Fettstein. 
Of this T have seen two descriptions; one by Haity, in his 
Tableau Comparatif; published last year; and another by 
Count Dunin Borkowski, published in the 69th volume of 
the Journal de Physique, and translated in Nicholson’s 
Journal, (vol. xxvi. p. 354). The specimen, called Swedish 
Natrolite, in Mr. Allan’s possession, agrees with these de- 
scriptions in every particular, excepting that its specific 
gravity is a little higher. Borkowski states the specific. 
gravity of fettstein at 2-563; Haiiy at 92-6138; while I 
found the specific gravity of Mr. Allan’s specimen to be 
2°779, and, when in small fragments, to be as high as 2*790. 
This very near agreement in the properties of the Swedish 
natrolite, with the characters of the fettstein, leads me to 
suppose it the substance to which Werner has given that 
name, This opinion is strengthened by a fact mentioned 
* It has been observed also, by Professor Jameson, in the fletz-trap rocks 
behind Burntisland. 
by 
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