12 HINTS FOR OFFICERS IN THE DETECTION OF PRECIOUS STONES. 
r 
other corundum gems. But this will not be appreciable to the experi- 
menter, who will scarely succeed in scratching a ruby with a sapphire, 
under any conditions. 
If the searcher cares for a more elaborate outfit for testing hardness, 
I have no doubt that Mr. Streeter would willingly make him up a case 
containing pieces of diamond, sapphire, topaz, quartz, felspar,and apatite. 
A reference to the table will show how these might be used. Each would 
scratch all stones below it—more or less easily, as they are placed in 
the table. Thus felspar would barely scratch opal, but would scratch 
sphene pretty readily. The reader will see that by locating his stone 
between two of his test pieces—say “scratched by topaz—scratches 
quartz” he will have narrowed its possible identity within very small 
limits, and will probably be able to name it from its colour or crystal- 
lization (Table 1V.). If he still cannot do this he had best resort to 
specific gravity (Table IIT.). 
Specific gravity is very easy to find—theoretically. You weigh your 
stone in air, then in distilled water, and say— 
Weight of stone in air (weight of stone in air—weight of stone in 
water) = specific gravity of stone. Nothing is simpler, if your stone 
weighs a few ounces and you have a good spring balance. But if, as 
is generally the case, it weighs a very few grains—then you cannot 
get on, without an apparatus that would cost several pounds, and be too 
delicate and bulky to carry about. So you resort to heavy liquids. 
I give a list of several of these, but not full details, as I can only 
recommend the last for reasons given :— 
“ Sonstapi’s SoLution.” 
Solution of iodide of mercury in iodide of potash. Exceedingly 
poisonous and corrosive ; dangerous to have in a house. Stones must 
be inserted with steel pincers. In hot climates a specific gravity of 
3°17 is obtainable, but not in England, so far as my experiments go. 
“ RoHRBACH’S SOLUTION.” 
Solution of iodide of mercury in iodide of barium. Very poisonous. 
Decomposes on addition of water, so troublesome to vary. Highest 
specific gravity obtainable = 3°588, 
“ Braun’s Murayzene Jopipz.”’ 
Has to be diluted with benzole, not water, and kept in the dark, 
with a globule or two of mercury in it. Price about 4s. the ounce. 
Highest specific gravity obtainable = 8°33. 
*Murayiene Iopipz, wita Iopororm aNp Topinz.” 
Unstable and messy. Highest specific gravity obtainable = 8°65. 
‘‘TopIDE oF SitveR and Nitratre or Srinver.”’ 
Liquid at 70° centigrade. Specific gravity =5. Too great for our 
use. 
‘CHLORIDE oF Zinc AND CHLORIDE oF Leap.” ee. 
By melting these together, and varying the ingredients, liquids of 
