378 
Examination of the Minerals, fyc. 
[Dec. 
oxydes themselves, on a flux of borax, I obtained a satisfactory explanation of the 
difficulty which had arisen from placing implicit confidence in book authorities. 
Pure oxyde of copper yielded invariably a blue glass, varying in depth, accord- 
ing to the quantity present in the assay ; while hot, it was at first red, then emerald 
green, but it always became blue on cooling. 
Pure oxyde of iron gave an umber coloured glass, hardly visible with minute 
portions, and increasing to a deep red brown, with more of the oxyde. 
The mixed oxydes of copper and iron yielded every variety of green, as might 
have been expected, from the former results : with minute portions ot the two, 
neutralization of the colours, ( umber and blue being nearly complementary to 
one another) seemed to take place; and the glass was less coloured than « it 1 
either of the oxydes alone ; the depth of shade, therefore, is not a perfect test o 
the quantity of each metal present : yet, with a standard set of prepared S 
the blowpipe examination might be rendered capable of affording fl u ; in 3 a ’ sg 
results with greater accuracy than any other method, considering the minu en 
of the specimen operated upon. . V{ j e 
The genuine, or precious turquoise appears, then, to be coloured wholly 3 ' ce0 f 
of copper; and as the mineral becomes tinged with green, it is in in etal 
contamination with oxycle of iron, until in the bright green variety the la ^ ^ 
greatly predominates. It may be remarked how perfectly this result cor ‘° 
observation of the native miners, that the green colour is caused by tae 1IU ^ r . t j g 
tion of zeng , which rather signifies vitriol, or sulphate of iron, than e being 
translated by Mr. Fraser. The miners are also correct, as to the tart o , ^ ur ^, o0 d : 
no considerable ore of copper among the mineral products of the neig 11 ^ iron 
the blowpipe does barely detect a trace of this inetal in the earthy sub 1 3,31 ^ aS been 
or decomposing pyrites, which may, probably, be the source whence 1 
acquired l»y the turquoise. . aD d esti- 
C. The third process of analysis was directed towards the separation 
nation of the constituent earths and oxydes of the turquoise. . c alcin at3011 
In its natural state, the mineral is not affected by the acids; but a , ^ pxP er * tneIlt f 
it becomes, for the greater part, soluble in them. The residue in fo'* 1 \ 0 xyde , 
varied from 5 to 6 per cent, and was found to consist of alumina an . ce of 
iron, with a small portion of silex. As it was impossible to free the sl3 j nC lined 
stones, in the first instance, entirely from their ferruginous crust, \ al s e videot / 
regard the wholeof the insoluble matter as extraneous ; more so, as ' g p ech uer3i ’ 
smaller in amount in proportion as more care was taken in selecting * 1 , 
for the mortar. 
The nitric solution, of a green tinge, being evaporated to incipient- ua disso^ ve ? 
redigested in boiling water, left the greater part of its earthy depos^ 1 ^ 
while the liquid itself remained turbid, as if holding the matter tak^ 31 chi e ^ 
in suspension. At first it was imagined that the deposit m uS ^ t p a t e ar ^ 
siliceous, since the above is the formula provided for the separate 13 the w ‘* 0 [0 
in.the humid analysis : either nilric or sulphuric acid, however, dis s ° add^[ 
nd 
without residue ; and when a proper portion of potash or ammoni a , crys ta 
the solution in the latter acid, the whole was converted into p ul , 0 ( 
oetohedral alum. . „roP eI ^ ... 
' . n iTli 
it hi i . «y 
It is worth while to draw the attention of the inexperienced to p 
or alkaline salt is present in the magma, the alumina will be ^Vfcoiol 305 ' 3 
addition ot water ; but the earth alone (for the nitrate seems to be 131 
simple drying) is by no means re-soluble in water. th r °' VD f c°P' 
Such part of the alumina as was still suspended in the liquid, beitfp ^yde . . die 
by ammonia, and the gelatinous precipitate (which was tinged with °' c i' e po 5lt ’ 
per) collected in the usual manner, dried, and added to the fff st 
i43l33133, r la Was found to weigh 7 grains, or 70 per cent. 
ortf 
a *■*&>*’ 
1). The blue ammoniacal solution evaporated to dryness, yielded d a , a ps 
or copper, with a slight glaziness, from a remnant of alumina, or 
weighing altogether 5,3 per cent. ■\gV eS 
previous test analysis had proved the total absence of glucina, *** rfO* 1 ’ 
cHnese » an ^ only a minute, if any, contamination of lime. So** 3 ^ put 1 
Rerne rally accompanied the ammonio-aluminous precipitn^’ 
T i v d to ! ,e *°reign matter above mentioned. ftef 
ou ing, therefore, the ingredients of genuine turquoise, to th£ 111 
