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MINERALOGICAL REMARKS. 279
mafs vaft numbers of fmooth, hard, in every way compreffed, obtufe¬
angular, roundifh, or longifh pebbles, which here imitate water¬
worn pebbles of fmoked quartz (Rauchtopa:), there drops of opake
enamel, lie enveloped and varioufly interwoven with, and furrounded
by, thefe leaves or fcales. ‘They are of the fize of à great or fmall
nut, though diet? much fmaller, even not bigger fometimes than
millet or peppy-feed.
““ Long ago thefe pebbles, or whatever you pleafe to call them,
were found in mufeums; and when I was in Siberia, the fmoke¬
coloured tranfparent kind were brought in abundance to Irkutz,
“where they were fold for polifhed {moked topazes. Yet I do not
find them mentioned by Steller in his Mineralogical Remarks,
although he was on the fpot, and has given an account of other
remarkable things. ‘The fine leafy mountain-rock, which fometimes
entirely forms little balls which have no other ftony nucleus, but are
compofed, to the very centre, of concave leaves lying one upon
another, and fometimes furrounds thefe pebbles, which we fhall next
defcribe, has the very remarkable and firiking property, without any
addition, to fwell up under the blow-pipe, with fome noife, as quick
as alum or borax, and to be changed into a fine white frothy light
and friable fubftance. If we increafe the blaft, it increafes in bulk,
_ till it is quite fpongy, and it then cannot by any means be brought
into a glafs bead, either with or without’ fluxes: fome pieces
crackle and fly before they are red hot, others do not.. This particular
effect
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