15 
susceptible of deterioration by action of light and exposure. 
It may be stated that for many years very few of the real 
Persian turquoises have found their way to Europe; the 
quarries having been closed except for Royal use in Persia. The 
majority of ‘‘ stones ” at present in use in Europe being artifical 
vitreous productions, and others cut from a substance known as 
Odontolite. Odontolite is a mineral formed from animal remains 
decaying in contact with sulphate of iron (iron Pyrites) under cer- 
tain conditions. ‘The sulphate of iron combines with the phos- 
phate of lime, in the teeth or bones of the animal, forming phos- 
phate of iron or vivianite. Where this process takes place in 
bones, the surface of the bone being naturally dull, the colour is 
a dull blue, but seen through the enamel of a tooth the colour is 
of a turquoise blue colour. 
I have attempted to imitate this process as follows :— 
Distilled water is thoroughly boiled so as to get rid of as much 
air as possible, and sulphate of iron dissolved in it, a clean 
deciduous incisor tooth of a calf is then placed in a bottle 
and the solution poured on. The whole is then well stoppered. 
In a few hours the colour of the tooth commences to change 
to a slightly greenish colour. Owing to animal matter 
detached from the tooth, causing the solution to appear 
milky, the solution is then changed, and this operation may 
be repeated as often as the solution is discoloured. In a 
few days spots and patches of a colour exactly resembling 
the turquoise colour of the specimen in question, begin to 
form in the pulp cavity of tooth below the enamel, and the 
portion so marked appears bright and clear through the surface of 
the enamel. So far 1 have been unable to obtain a specimen 
coloured so perfectly and evenly as the specimens produced. On 
each occasion some portion has changed to a rusty brown, owing 
I suppose, to air having been introduced into the solution. Un- 
fortunately the iron sulphate cannot be dissolved in spirit. 
The deciduous incisor of a calf is a particularly good subject 
for the experiment, as the front surface of the tooth is broad 
and regular, and susceptable of a high polish. The pulp cavity 
is also large and there is a greater presence of phosphate of lime. 
The Egyptians were acquainted with the art of dying teeth 
and bones with a solution of sulphate of copper, but the colour had 
a greenish hue, not so pleasing as that of the tooth of the calf 
produced. 
Copper was also probably used in staining the ivory handles 
of the knives and forks in use at the end of the last century. 
