fc> A SYSTEM OF 



Tied, and is found in Sunnerfkog's cop- 

 per mine in the province of Smoland *. 



SECT. LTV; 



F. The Flint, SiJfot pyromachus. Lapis comeus, 

 or Hornftei? of the Germans. 



This is equally ccmmon with the Quartz, 

 and It is full as difrlcuit to defcribe it: efoe- 

 cially as it forms a kind of intermediate fub- 

 ilance between Quartz and Jafper, both 



* That the colour in thefe latter bodies depends on metals, 

 is eafily proved by metallurgical Efiays, and the refemblancc 

 they have with compofitions of glafs, made on the fame prin- 

 ciple; but the fame cannot be affected of the precedent co- 

 loured quartzes (Seel. li. Hi.), before it be evidently demon- 

 flrated. 



It is very likely, that a quartz may be found which is inti- 

 mately mixed with a calcareous eartlu and fuch is, perhaps, 

 the Hungarian fparry quartz (Se6t. li. C), which, however, 

 1 recommend for further examination. 



The quartz in gcne/al, and especially its criftsls, are very 

 commonly thought, when yet in their foft or diflblved Hate, 

 to have included within th«rn fOiiae vegetables, for inftance, 

 grafs and napfs. This I Canrfot abfolutely deny, but I muft 

 at the fame time obferve, that it deferves. to be carefully ex- 

 amined, if that, which is fhewn as a grafs, be not an afbef- 

 tos, or a flriated cockle, and the mofs, only branched vacui- 

 ties filled with earth, wbicb, by their being ramofe, bear a 

 vegetable appearance : it is very common in agates, and 

 jnakes them of lefs value than otherwife they would be ; this i* 

 moft generally the cafe with thofe ftones, which are fhewn as 

 including vegetable*, and for my own part I have never been 

 fo fortunate as to meet with any others. 



When the rock criflals are femi-tnmfparenr, or intermixed 

 with opaque veins, they are, by the Swediih lapidaries, called 

 Milk criftals ; when they are found in form of round peb- 

 bles, which is occafioned by their being toiled about and 

 rubbed againfl: one another by floods, or by the fea, they 

 are called by the Englifh lapidaries, Pebble cryftals. They 

 •ome from the Indies, Siberia, and other places, but thefe 

 cannot be rangfd feparately, for evident reafons, or otherwife 

 tor r#afons already mentioned in their proper places. 



which 



