228 — Analysis of the Substance called Turquoise. 
It results from all the above experiments, therefore, that 
100 parts of turquoise contain, 
Phosphate of lime - - - 80 
in place of 82, found in the experiment E, de- 
ducting the above quantity of phosphate of mag- 
nesia, 
Carbonate of Jime - - - 8 
Phosphate of iron - - - 2 
of magnesia - his 1m 
of manganese (an inappreciable quantity) 0 
Alumine . - - - it 
Water and loss - - - - 6L 
Although I obtained similar products on examining se- 
veral turquoises, yet we cannot decide if they are identical. 
The turquoises that I made use of, were exactly similar to 
those in the cabinet of the Museum of Natural History; and 
M. Haiiy, whom I consulted, could not say that they were 
true Persian ones. M. Guyton thinks that there is a dif- 
ference between the Persian and European turquoises. In 
his lectures on mineralogy at the Polytechnic School he has 
for some years maintained that the former contains silex. 1 
Tt is possible they may contain this substance accidentally; ¥ 
but I never found any in those [ examined. Idonot think 
“that this difference ought to hinder mineralogists from clas- 
sifying turquoise. M. Guyton himself has already placed it 
among the fossil bones: this celebrated chemist has also 
made some comparative experiments: he saw that fossil 
bones assumed in the fire a colour analogous to that of tur- 
quoise ; that digested in water containing potash they be- 
came blue, and that this blue varied in shade and passed to: 
a greenish or deep blue; and lastly, that bones exposed to 
the air became white. . 
Messrs. Fourcroy and Vauquelin have also observed that 
bones calcined strongly often assume a blueish tint; this 
colour appeared to them to be owing to the presence of a. 
little phosphate of iron, 
Thus 
