Gems their Production and Colours. 43 
parency, and polifhed Sides and Angles, 
bear a near Refemblance, when enlarged 
by the Microfcope, to the Shootings (in the 
piffures of Rocks and Mines) of Spars, 
Cryftals, and feveral Kinds of angular and 
figur’d Gems, and ferve moreover to point 
out after what Manner fuch Bodies are alfo 
probably formed in a furrounding Fluid 
and poffibiy too of fimilar Materials : for 
there feerns nothing unreafonable in fup- 
pohng that different mineral Salts, difTolv- 
ed in fome Fluid exfuding from Rocks 
or Mines, and tinged with metalline Mat¬ 
ter, may, through the wonderful Chemif- 
try of Nature, fupply the different Sub- 
Ranee, Hardnefs and Colour of Spars, Cry- 
flals,' and precious Stones 3 in fome fuch 
like Way as their Refemblanc'es are pro¬ 
duced from the Solutions of. fuch Salts J. 
Nor are the Hardnefs of precious Stones, 
their 
* Cryftals and all angular Bodies concrete in the Mid ft 
of a refolvent Fluid or Menllruum. The Fluid wherein 
Cryftal is concreted, is to Cryftal as common Water is 
to Salt. (S/eno’s Prodromus, Eng. Edit. Page 64.) That is, 
the Cryftal Particles are feparated and float in fuch Fluid, as 
the Particles cf Salt do, when diffolved in common Water. 
t Mines, or Beds of Metal, are met with conftantly, if 
fought after, near the Places where precious Stones are 
found. The Ruby is fuppofed by fome to take its Teint 
from Gold, by others from Iron ; the Emerald and Sapphire 
from Copper, but by different Menftrua ; the To pas; from 
Lead or Iron, Granates from Iron, &c. and a Mixture of 
two or more Teints from different Metals may poffibiy give 
Colour to the Amethyft, the Hyacinth, the Opal, &c. A 
greater or left Proportion of metalline Matter may alfo ren¬ 
der the Gem deeper or paler, harder or fofter. 
When 
