the HeJJian Pyrites, 355 



face. In this pipe-earth, which is dug very deep* 

 are fometimes found fofifile galls over the pyrites* 

 or at leaft foreign fruits entirely refembling galls* 

 In the greyifh crucible-earth are alfo found fat* 

 pbttr-pyrites, though feldom, and in fmall bits and 

 grains only, but which the crucible- makers care- 

 fully pick out from among the clay, becaufe if 

 left behind, they would render the vefTel, made 

 from the clay, perforable in a ftrong heat, and 

 unfeiviceable : of this pyrites the workmen affirm 

 it refolves in the air to vitriol : tho' very (lowly, 

 the dark grey potter's clay is properly that earth, 

 which holds the famous minera martis folaris, thus 

 magnificently ftyled by Glauber. The place, 

 where thefe pyrites are found, is at the foot of a 

 hill, not far from the * village •, where, together 

 with the faid potter's clay, in which they lie flrew- 

 ed up and down with fome other coagula or drufe 

 of Mufcovy-glafs, they are dug out at a fmall 

 depth, almofl at the day, and found in fuch plenty* 

 that I myfelf, and two other perfons, had in about 

 one hour and half, with eafe, gathered a centner of 

 them : their figure generally, as that of the like 

 coagula, is more or lefs round, alfo oval ; exter- 

 nally they are of a blackifli caft, but internally of 

 ytllowifh, mod frequently of a paler, but fometimes 

 alfo of a darker hue than other pyrites ; and in 

 gravity and hardnefs differ nothing from the other 

 pyrites abovementioned. Only in this they feem 

 to have fomething peculiar, that they not only en- 

 tirely, but alfo (which chiefly deferves to be-con- 

 fidered ) very foon refoive fpontaneoufly in a moift, 

 open air, and crumble to a greyifti powder, which 

 after elixation and evaporation, yields forth a green 

 iron-vitriol, and an acid liquor. 5 Tis true, I am 

 acquainted with pyrites enough, which in time 

 ehange to a vitriolic fait ; as fuch are found in 



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