Oldal 30 [30]
280 MINERALOGICAL REMARKS.
effet of fire, with perfe& infolubility in acids, drew fir my atten¬
tion to this fubftance, and induced me to requeft Mr. Lowitz,
apothecary, and member of our academy, to undertake the chemical
analyfis of it; which I fhall fubjoin, after ] have deferibed the great
and fmall pebbles, which are contained in it in quantities as ina
pudding ftone.
“ Thefe pebbles, according to the {pecimens’ which have been fent
me, are of two kinds: one kind is juft like water-worn polifhed
fragments of {moked cryftal, commonly called fmoked topaz, and
was at firft confidered as fuch; but in polifhing it is feen immediately
that they are much fofter, and they readily crack; they are feratched
with the file, and fly when ftruck with a fteel, with which they how¬
ever give fire if ftruck on a fharp edge ; yet they are hardly to be
broken when ftruck with great violence with a hammer. Many
are uniformly clear, tinged (clouded) of a yellowith fmoke colour,
which is hardly obfervable in very {mall ones; others have very
evident, yet fine ftreaks or beds of a darker footy {moke colour. Thefe
more or lefs fine, and quite parallel, beds ran completely through the
ftone, and are in fome more abundant and crowded together, in others
lefs frequent, and render the ftone more or lefs cloudy. - In one of
thefe ftones I have found, on one of its fides, near the furface, an
oval footy {pot with a curved furface like a thin leaf grown in it.
The fhape of thefe pebbles is generally irregularly round or oval,
more feldom oblong, but always amorphous through various fuper¬
ficial
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