MINERALOGY. ^ 73 
A, In feparate or diftinft rhomboidal 
criftals, from the iron mine called MofT- 
grufvan, at Norbery in Weftmanland 
SECT. LXVII. 
O B S E R. V AT I ON OH the S I L I C E O U S O R D E R; 
The oeconomical tifes of this order are not 
fo manifold as thofe of the Calcareous and Ar- 
gillaceous claiTes ; however, moral reflexions laid 
afide, it will be neceflary briefly to mention' how 
far this order is confidered and employed in com- 
mon life. 
The Europeans have no farther trouble with 
the precious Hones, than either to cut them from 
their natural or rough figure, or to alter them, 
when they have been badly cut in the Indies ; in 
which latter circumftance they are called Labor a : 
and it may be obferved, that for cutting the 
ruby, fpinell, balias, and chryfolite, the oil of 
* This fpecies is very feldom found alone in form of 
veins, and liill more rarely as confiituting ihe fubftance of 
whole mountains ; but is generally mixed either with quartz 
and mica, as in the granites, or with jafper, having fome 
occafional concurring particles of quartz, cockle, and horn- 
blende, as in the porphyry. If the rhombic quartz and jafper 
were of the fame fpecies, that fort of porphyry which is 
made up of thefe two bodies only, ought to be ranked among 
the jafpers, inllead of being placed widi the Saxa in my 
i^ppendix, Se6l. cclxvi. 
It is however obfervable on old monuments, which are 
expofed to the open air, that though the porphyry has de- 
cayed, and confequentiy loll its poliih, yet grani^p of the 
fame age, compofed for the moft part of rhombic quartz, 
has kept its ludre. This, however, does not contradict 
the polTibility of rhombic quartz being cf the fame fubftance 
as the jafper ; becaufe the calcareous fpar is found to bear 
the weather, and even hre, better than the limeHone. 
vitriol 
