known by the Name of Turquorse. 295 
supply us with a method of distinguishing the turquoises of 
Persia from those of Europe. Aqua-fortis does not act upon 
the Persian ones; whence it follows, that these two kinds 
of stones, although similar in appearance, are nevertheless 
of a very different nature: it would be wrong, however, to 
draw an inference disadvantageous to our turquoises from 
this circumstance, or to think them more brittle. 
<¢ Aqua-regia, also, acts differently upon these two sorts 
of stones. It entirely dissolves the European, andr educes 
the Persian to a kind of paste whiter than the stone itself 
was, but which, however, is not deprived of all the blue 
colour. 
‘<< In general, these stones have a singular fault; their 
colour changes through time, without any solvent: their 
blue colour imperceptibly assumes shades approaching to 
green ; and they latterly become entirely green; while the 
colour of all the other precious stones is unalterable. When 
the turquoise has become green, it is no longer of any va- 
lue; for it is not yet the fashion to esteem this stone when 
it becomes green.” 
Chemical Examination of the Turquoise. 
Physical Characters.—Specific gravity, 3°127. Colour, 
clear green and blue. Hardness, a slight degree harder 
than glass; very difficult to pound; its powder is of a 
greenish gray, and its fracture is smooth. 
Chemicul Characters. —Exposed to the blowpipe it loses 
its colour and becomes of a grayish White, but does not 
melt. Heated in a platina crucible it assumes the same co~ 
lour, but becomes friable and is easily reduced into powder. 
In this experiment it loses six per cent. of its weight. The 
nitric and muriatic acids dissolve turquoise entirely. The 
solution made by the muriatic acid is yellow; that by the 
nitric acid is colourless. , 
The nitric solution presented the following phenomena: 
1. With lime water, a white flaky precipitate. 
2. With ammonia in excess the precipitate was of the 
same colour, but more abundant. The liquid above it ac- 
quired no blueish tint. 
Vol, 26. No, 103. Dec, 1806. P 3. Car- 
