MINERALOGY/ 71 



Langbanfhyttan in the province of Wer- 

 meland, and at Sponwik in Norway. 

 c. Yellow, from Bohemia. 



This laft mentioned, when calcined, 

 is attracted by the load-ftone, and being 

 affayed, yields 12 to 15 per cent, of 

 iron. 



* Jafper, when frefh broke, fo nearly refembles a bole of 

 the lame colour, that it can only be diilinguifhed by its 

 bardnefs. In the parifh of Orfa, in the province of Dalarne, 

 there is a red bole found in fpaces like glands or kernels, in 

 that fort of fandftone from which grindi'tones are cut ; and 

 fome miles diflant, in the rocks at Serna, a red jafper of the 

 fame colour and textuie as the above bole, is found in a 

 much harder kind of fandftone. In other places jafper is 

 found in fuch uncluous clefts, as if they had.contained unc- 

 tuous clays; as pipe clays, and red chalk :- and there are 

 Jikevvife feme jafpers which imbibe water. May it not then 

 be fuppofed with fome probability, that jafper is an indu- 

 rated bole, a reddle, or terre verte ? That jafper, as well as 

 thefe, confiih of clay and iron ; though, by reafon of its 

 being hardened, it becomes as difficult to extract thefe prin- 

 ciples from it, as to reduce a fmall quantity of fcorified iron 

 to its metallic form, when mtlted with a large quantity of 

 flag or glafs r That the fame bole or clay, together with 

 another fubftance, perhaps lime, after being diftolved by a 

 menfiroatn, not yet determined, is fufficient far the produc- 

 tion of flint flone ? and that fo much of the bole as was 

 fuperfluous, being feparated from the maf>, is found ad- 

 hering to the furface, or in the fifTures,&c. 



Thus one might imagine, that jafper could eafily be pro- 

 duced, and that the foft kinds might become harder by 

 length of time ; but its particles cannot be fuppofed to ap- 

 proach nearer and nearer to one another during the harden- 

 ing ; nor can it be imagined, that the jafper mould by that 

 means become of a finer texture. On the other hand, we 

 know extremely we J, and have the experience of it every 

 ere, that porphyry in the rocks decays into a white cruft, 

 wherever it is expoied to the air, although internally it re- 

 mains very hard and black; for inftance, at Klitten, in Eif- 

 dalen, in Sweden. From whence it may be fuppofed, that 

 water, which wafhes off the mouldered particles, muft by 

 degrees collet them fome where, and at length prefent us 



F 4 1 with 



