Oldal 29 [29]
OCR
MINERALOGICAL REMARKS. 279 mafs vaft numbers of fmooth, hard, in every way compreffed, obtufeangular, roundifh, or longifh pebbles, which here imitate waterworn 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 fmokecoloured 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 27
