eminently
sympathetic as to grow pale when its wearer is sick, or sorry ; and
similarly to straightway lose all its beauty if bought, and not
bestowed as a gift. Turquoises are valuable ; and, being so, are often
imitated ; their main composition consisting of phosphoric acid, and
protoxide of iron ; (though chemists differ as to the more absolute
composition) ; which being understood, clever rogues tinge the teeth of
fossil animals with phosphate of iron, professing to sell a grand set
of turquoise ornaments, and taking for the same a frauduÂlent price, at
the cost to themselves only of cheap old ivory. Artificial Turquoises
may be readily distinguished from the real by acids, and fire ; the one
discharging all the colour, the other burning up the supposed Gem
outright, leaving a nasty odour of burnt bone, as the only result of a
bad bargain.
Additionally,
respecting the Turquoise, the finest variety of this beautiful blue,
(or bluish-green) mineral, so highly valued as an ornamental Gem,
occurs in Persia ; from which territory the Stone first came to Europe,
by way of Turkey; thus getting to be named " Tuschesa " by the
Venetians who imported it; and by the French, " Turquoise." It is
chemically a hydrated phosphate of Aluminium, associated with a
variable proportion of hydrated phosphate of Copper ; to which latter
constituent it owes much of its colour. The green tints of certain
varieties appear to be further due to admixture with salts of iron. A
fine blue TurÂquoise analysed by Professor A. H. Church, yielded
alumina, 40-19 ; phosphorus pentoxide 32-86 ; water 19-34 ; cupric
oxide 5-27 ; ferrous oxide 2-21; and manganous oxide 0-36.
The most valued tint of the Turquoise is a delicate
