OCCURRENCE OF PRECIOUS STONES IN N.5S.W. 267 
often contain some zircon. The mistake is a pardonable one, for 
the surface lustre of these stones is often finer than that of a 
diamond, and as is well known, the specific gravity of the zircon 
is 4-7, while the diamond has a specific gravity of 3-5 only. 
To distinguish between these stones the prospector will try if 
the supposed diamonds will cut glass. As a zircon when used to 
advantage will scratch glass easily, while a true diamond will not 
mark glass if a rounded face is drawn along the glass. Serious 
mistakes are thus apt to occur. Quite recently money was lost 
and much suffering caused through a “find” of white zircons near 
Nundle being mistaken for diamonds. 
In diamond bearing country I should advise a prospector to 
carry a small plate of sapphire and a splinter of diamond mounted 
on the end of a short length of stout brass wire. This last is 
knownasa writing diamond. The sapphire plate and the diamond 
should not cost many shillings. 
The supposed diamond is set in the end of a stick of sealing 
wax, and while the wax is softened by heat the stone can be so 
arranged that a sharp solid angle or a edge projects. This can 
be done after a little practice by heating the stone, and quickly 
transferring it to the wax. Holding the stick of sealing wax, the 
Stone to be tested is rubbed with a gentle pressure round and 
round, on the polished face of the sapphire plate. Not more of 
the sapphire need be used than the space covered by a pin’s head. 
After the friction is continued for half a minute, if the sapphire 
plate has lost its polish, and with a lens shows the point of contact 
“eaten into” or “ burned,” the stone being tested is a diamond, 
since the diamond is the only stone that can cut into a polished 
plate of sapphire. 
The use of a writing diamond will however settle the matter at 
Once. Ifa prospector draw a writing diamond over a smooth 
zircon and over an uncut diamond, the difference will be so 
“pparent that there can be no room left for doubt. Even << 
® very gentle pressure the writing diamond “catches” or “ 
