16 HINTS FOR OFFICERS IN THE DETECTION OF PRECIOUS STONES. 
shades of colour, etc. that none buta professional can really value them. 
I have been studying gems for several years, and I would not dream 
of purchasing a large diamond, sapphire, or ruby, at anything like the 
market price for such stones, on my own judgment. The curious 
thing is that the jewellers themselves know, as a rule, very little 
indeed of most stones. I got a pink pearl in Barbados 67 grains in 
weight, and rose pink in colour, and I got a different opinion upon it 
from almost every jeweller to whom I showed it in London. Perfect 
flawless stones have a pretty definite value in the market; but they 
are infinitely few, and the moment the colour falls off, or a flaw, how- 
ever minute, appears, it becomes seemingly entirely a matter of opinion 
how much this detracts from the value of the gem. Should any of my 
readers be fortunate enough to make a discovery of precious stones, I 
can only advise him to throw himself upon the mercy of Mr. Streeter, 
Watherston & Co., or some other first-class jeweller, and take what he 
is offered, which might be about half what the cut and mounted stone 
will fetch. 
I have not referred to opaque stones in this paper, as they are none 
of them of much value as gems, and are perfectly easy to distinguish 
by eye. The turquoise is an exception. The stones which might be 
taken for it are odontolite, callainite, and chrysocolla or silicate of 
copper. Odontolite is fossil ivory stained by phosphate of iron or 
copper. It is of some value. Softer than true turquoise, and emits 
an odour when heated. Callainite is so soft as to be scratched with 
a penknife. Chrysocolla is also soft and has a specific gravity of only 
about 2°2. 
The most hopeful geological formations in which to search for 
precious stones are the primary, non-fossiliferous rocks, and their 
derivatives, but they may occur almost anywhere. Where diamonds 
are found gold is generally present for some unknown reason. ‘The 
only diamond ever found in Kurope was picked up by an Irish peasant 
girl, amongst the pebbles of a little stream at Maguire’s Bridge, 
Fermanagh, Ireland! It is supposed to have got there in the crop 
of some migratory bird. Fowls are very fond of swallowing bright 
stones, and their gizzards and crops might be examined in a new 
place. Pebble beds near mouths of rivers are perhaps the best 
hunting grounds of all. 
Precious opal can be distinguished at a glance. Very often a stone 
of this kind which has lost its brilliancy can be improved by hanging 
it up near a water tap (not, of course, wnder it), and leaving the tap 
running for 24 hours or so. 
If any reader of this short paper should become really interested in 
the subject, I wouldrecommend him to purchase the following books 
—in addition, of course, to Professor Church’s Little Hand-book. 
“DIAMONDS AND Precious Stronges, py H. Hmanven.” 
Publishers “ Chatto and Windus,” price 6s. This is an excellent 
practical treatise, and contains valuable tables and illustrations of the 
crystalline forms of many gems. As regards prices, it is somewhat out 
of date, but otherwise one of the best works I know on the subject. 
