Oldal 30 [30]
OCR
280 MINERALOGICAL REMARKS. effet of fire, with perfe& infolubility in acids, drew fir my attention 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 however 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 fuperficial 28
