A SYSTEM OF 
l^ed, and is found in Sunnerlkog’s cop- 
per mine in the province of Smoland 
SECT. LIV.‘ 
F. The Flint, Silex pyromachus. Lapis corneuSj 
or Hornjlein of the Germans. 
This is equally common with the Quartz, 
and it is full as difficult to defcribe it ^ efpe- 
cially as it forms a kind of intermediate fub- 
Itancc between Quartz and Jafper, both 
That the colour in thefe latter bodies depends on metals, 
is eafily proved by metallurgical Eiiays, and the refemblance 
they have with compolitions of glafs, made on the fame pr^- 
ciplc; but the fame cannot be affedtcd of the precedent co- 
loured quartzes (Sed. ii, lii.), before it be evidently demon- 
Hrated. 
It is very likely, that a quartz may be found which is inti- 
mately mixed with a caicaieous earth, and fuch is, perhaps, 
the Hungarian fparry quartz (Scft. li. C.), which, however, 
I recommend for further examination. 
The quartz in general, and efpccially its criftals, are very 
commonly thought, when yet in their foft or dHTolved Hate, 
to have included within them feme vegetables, for inflance, 
grafs and mofs. This I cannot sbfolutely deny, but I muft 
at the fame time obferve, that it deferves to be carefully ex- 
amined, if that, w^hich is Ihewn as a grafs, be not an a^ef- 
tos, or a Hriated cockle, and (he mofs, only branched vacui- 
ties ill led with earth, w'^^hiefc, by their being ramofe, bear a 
vegetable appearance : it is very common in agates, and 
makes them of lefs value tlian otherwife they would be ; this is 
mod: generally the cafe with thofe Hones, which are fiiewn as 
including vegetables, and for my own part I have never been 
fo fortunate as to meet with any others. 
When the rock criHals are femi-trlinfparent, or intermixed 
with opaque veins, tli^y are, by the Swedifh lapidaries, called 
Milk criHals ; when they are found in form of round peb- 
bles, which is ocesdioned by their being tofied about and 
.rubbed againH one another by Hoods, or by fhe fia, they 
are called by the EngHfh lapidaries. Pebble cryHals. They 
come from the Indies, Siberia, and other places, but thefe 
cannot be ranged fepm-ately, for evident reafons, or otherwife 
ior rtafons already mentioned in their proper places. 
v/hicK 
