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MINERALOGICAL 
OBSERVATIONS. 
TIN ORES. 
VSTHETHER true native tin has 
" " ever been found, as fome mineralo¬ 
gies have aflerted, is a queftion not yet 
determined, even in Cornwall. On 
the contrary, it is rather thought that 
thofe pieces of metallic tin, which have 
been found there, are only a produ&ion 
of art. 
The common tin ores are in a calci- 
form, and at the fame time indurated 
glafs-like ftate, more or lefs mixed with 
calx of iron, and commonly joined alfo 
with ores of arfenic. Zinjiein, (Tin- 
ftone,) might be the general denomina¬ 
tion of them, but commonly only the 
B 3 irregular 
