New Publications. 83 



Chemical Examination of the Elajlic Quarz* , (Sand-Sbiefer, 

 flexible Sand-Jlone,) from Brazil. 



The Angular elaftic flexibility, fo feldom occurring in the 

 mineral kingdom, in which this follil, in iti form and ap- 

 pearance, refembles novaculite (Turkey hone), has attracted 

 the attention of naturalifts, but at the fame time has led 

 many pcrfons to doubt its exiftence as a natural fubftanee, 

 and to fufpeSt that this may probably be a product of art. 

 It comes from Brazil, near Villa- rica, the principal town 

 of the province of Minas Geraes, which fact was, for a 

 while, kept a fecrct. There it occurs in not very thick 

 itrata, whofe hanging and (hading fides are cafed over by a 

 gray cruft of} inch thick ; and from thence it was brought 

 to Portugal the fir ft time, in the year 1780^ by the marquis 

 de Lavradio, viceroy at Rio de Janeiro. Among the fpeci- 

 mens I have feen, that of the imperial cabinet at Vienna, 

 fo remarkable for its precious foifils, is by far the greateft ; 

 it being 26 Vienna inches long, 16 inches broad, and 1 inch 

 thick. It is, however, probable that this (lone, together w r ith 

 its remarkable phyfical property mentioned before, was al- 

 ready known in the fixteenth century; and that it is the fame 

 with that defcribed by GafTendi, in Vita Peire/kiif, in the 

 character of a flexible whetftone (novaculite); as fuggefted by 

 the authors of the GoUingifche Gelehrte Anzeigcn, when this 

 (lone has again been brought into notice J. 



On infpecting with a microfcope the homogeneous or in- 

 tegrant parts of which this elaftic ftone is aggregated, and 

 which may be eafily feparated by compreffure or levigation, 

 I found them all alike; that is, they were all flat, longifh 

 plates or fcales, perfectly clear and pellucid. All their dif- 

 ference confifted in the variety of their outlines; fome trun- 

 cated more fharply, others more obtufely ; others longer, 

 but very thin; while others were broader and (liorter; but 

 mod of them I perceived on one or both fides notably finu- 

 ated. I am inclined to think, that the elafticity of this foflii 

 originates folely from the form of its aggregation. For, as 

 may be diftinctly feen at the firft glance m the entirettone, 



* Schriften der Berliner Gefellfchaft Naturforfchender Freunde, b. vi. 

 1785, p. 32z. — TWS miners indicate by thefe expreffions the greater or 

 kfs Hope in the ftrata, though chiefly with reference to rake- veins, pot 

 fully perpendicular. The hanging fide is that toward the day, and is alfo 

 called banger; and the hading ride, which fikewife goes by the name 

 ledger^ is the under one next to tM*ed of the tlratum. See Williams's 

 Natural Hi ft or \< of the Mineral Kingdom, Svo. Edinb. 1789. vol. i.p. a6g» 

 Tran 11. 



f Libr. iv\ ad annum 1630. p. 2.54. edit. 1706. 



+ Of the year 1784, No. m. 



F* all 



