UC-NRLF B 14

GEMS AND PRECIOUS STONES. 19
Its value cannot be estimated. This diamond was obtained at a cost of
8 dollars per carat, for it was obtained under contract with a lot of other
stones. Had it not been discovered until six hours later those who secured
it would not have received it, for the contract would have expired.
The "Porter-Bhodes" diamond was found Feb. 12th, 1880, in the Kim-
berley mine. It weighed in the rough 150 carats, and its estimated value is
200,000. It is of a very fine lustre.
The " Stewart" diamond was one of the earliest large diamonds found in
the South African fields, its weight in the rough was 288| carats. It is of a
light yellow tinge. It was found in the year 1872.
The " Jagersfontein," a diamond weighing, in the rough, 209^ carats was
obtained in this locality ;
it was stolen, but recovered by the owner.
The " Du Toit I" and " Du Toit II," the first a gem weighing 244 carats
when cut, the other weighed in the rough 124 carats. These were obtained
at Du Toit's Pan.
The " Star of South Africa," better known as the " Dudley," weighed in
the rough 83 carats, by cutting it was reduced to 46 f carats. It is the
property of the Countess of Dudley. It is the diamond obtained by Van
Niekirk from a native in the early days of the diamond fields.
Besides this list, there are a great many other large diamonds of historical
interest that have been obtained from the various diamond fields of the
world, many of these gems
character.
are connected with deeds of crime of the worst
.
CORUNDUM,
and its gem varieties, Ruby, Sapphire, Amethyst, Emerald, Topaz,
Aquamarine, and Asteria.
To distinguish these from other minerals bearing the same names they are
" "
Oriental topaz," Oriental amethyst,"
known as Oriental, thus :
"
Oriental emerald," " Oriental aquamarine," and " Oriental ruby."
Originall3 r the words Oriental and Occidental were applied literally, but
now they are used to simply establish the superior quality of the gem or
otherwise, so that Oriental ruby means the true ruby.
Crystalline system = Hexagonal.
Hardness = 9.
Specific gravity = 8'9 4'16.
Lustre = Vitreous, sometimes pearly on the basal planes.
Cleavage = Basal ; that is at right angles to the principal axis of the prism ,
sometimes perfect.
Composition = Pure Alumina (A1 2 O 3) Aluminium 53'4, Oxygen 46'6 per
cent.
Inferior corundum (not considering emery) contains in some instances as
much as 15 per cent, of impurities, these being iron, lime, magnesia, and
silica.
Prom a mineralogical point of view the different colours of the varieties of
corundum are of no account, as it is the physical properties and chemical
composition that determine the species, and chemistry has not yet enabled
us to arrive at a satisfactory conclusion as to the cause of the differences of
colour in the several varieties of this mineral. That the colour is derived
from the presence of minute quantities of metallic oxides appear certain, but
this does not account for the blue colour of the sapphire, or the red of the
ruby ; yet it is these very colours that determine the value of these gems
and assists to place them in the category of precious stones.