388 On SODALITE, a new 
fented rectangular prifms, terminated by planes, meafuring, 
with the fides of the prifm, 110° and 70° or nearly fo,—a 
form which belongs to a rare mineral, known by the name of 
Sahlite, from Sweden. He further obferved, intermixed along 
with this, another material ; and after fome trouble, fucceeded 
in detaching a mafs, prefenting a regular rhomboidal dodecahe- 
dron. It was to this form that Mr ALLan had previoufly re- 
quefted his attention. 
SomE time before this inveftigation, M. de Bournon had 
examined a mineral from Sweden, of a lamellated ftru@ture, 
and a greenifh colour, which, he found, indicated the fame 
form. From this circumftance, together with fome external 
refemblance, which ftruck him, he was induced to conclude, 
that our mineral was a variety of that fubftance. 
To that fubftance the name of Swedith natrolite had been gi- 
yen, in confequence of the inveftigation of Dr WoLLaston, 
who found that it contained a large proportion of foda. 
THERE are few minerals, however, that are fo totally diftinc 
in their external characters as the natrolite of KLAproru, and 
the fubftance we are now treating of. The mineral examined by 
KLAPROTH occurs at Roegan*, on the Lake of Conftance, in 
porphyry-flate, coating the fides of veins and cavities in a ma- 
mellated form, the texture of which is compaét, fibrous, and ra- 
diated ; the colour pale yellow, in fome places pafling into 
white, and marked with brown zones. Hitherto it had never 
been found in a ftate fufficiently perfect to afford any indi- 
cations of form. Lately, however, M. de Bournon was fo 
fortunate as to procure fome of it, prefenting very delicate 
needleform cryftals, which, by means of a ftrong magnifier, 
he was able to afcertain, prefented flat re@angular prifms, ter- 
minated by planes, which, he thought, might form angles of 
60° 
* Ir has been obferved alfo by Profeflor JamEsoy, in the fletz-trap rocks 
behind Burntifland. 
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