NOTEWORTHY DIAMONDS
Prodigious diamonds are not so uncommon as is generally supposed.
Diamonds weighing over an ounce (151·5 carats) are not unfrequent
at Kimberley. Some years ago, in one parcel of stones, I saw eight
perfect ounce crystals, and one stone weighing 2 ounces (Fig.
12). The largest diamond from the Kimberley mines weighed 428½
carats, or nearly 4 ounces troy. It measured 1⅞ inch through the
longest axis and was 1½ inch square. After cutting it weighed 228½
carats, losing 200 carats in the process. The largest known diamond
was discovered in January, 1905, at the New Premier Mine, near
Pretoria. This mine is of the same type as the Kimberley mines, but
larger in size, and, in fact, is the largest known diamantiferous
pipe in the world--the pipe containing the “blue ground,” along
the longer diameter of its oval-shaped cross-section, measuring
over half a mile, and its area is estimated at 350,000 square
yards. This pipe breaks through felsitic rocks. The diamond, called
“Cullinan” from the name of one of the directors of the company
on whose farm it was discovered, was presented to King Edward on
his birthday by the people of the Transvaal. It weighed no less
than 3025¾ carats, or 9586·5 grains (1·37 lb. avoirdupois). It was
a fragment, probably less than half, of a distorted octahedral
crystal; the other portions still await discovery by some fortunate
miner. The frontispiece shows this diamond in its natural size,
from a photograph taken by myself. I had an opportunity of
examining and experimenting with this unequalled stone before it
was cut. A beam of polarised light passed in any direction through
the stone, and then through an analyser, revealed colours in all
cases, appearing brightest when the light passed along the greatest
diameter--about 4 inches. Here the colours were very fine, but
no regular figure was to be seen. Round a small black spot in
the interior of the stone the colours were very vivid, changing
and rotating round the spot as the analyser was turned. These
observations indicated internal strain.
[Illustration: FIG. 12. A GROUP OF LARGE DIAMOND CRYSTALS.
To face p. 76.]
The clearness throughout was remarkable, the stone being absolutely
limpid like water, with the exception of a few flaws, dark
graphitic spots, and coloured patches close to the outside. At one
part near the surface there was an internal crack, showing well
the colours of thin plates. At another point there was a milky,
opaque mass, of a brown colour, with pieces of what looked like
iron oxide. There were four cleavage planes of great smoothness and
regularity. On other parts of the surface the crystalline structure
was very marked. The edges were rounded in parts, and triangular
markings (depressions) were to be seen. I also noticed square
depressions, nearly as sharp and perfect as the triangular ones.
The cleaving and cutting and polishing of the Cullinan diamond
was entrusted to the firm of Asscher and Co., in Amsterdam. The
cleavage of the diamond was very successfully accomplished by Mr.
Joseph Asscher. An incision half an inch deep was made with a sharp
diamond point in the proper place, then a specially designed knife
blade was placed in the incision and it was struck a heavy blow
with a piece of steel. The diamond split through a defective spot,
part of which was left in each portion of the diamond.
Gigantic as is the Cullinan diamond, it represents in weight less
than half the daily output of the De Beers mines, which averages
about 7000 carats per day.
Next in size to the Cullinan comes the one which was found at the
Jagersfontein Mine. It weighed 970 carats--over half a pound.
The following table gives the names and weights of some historic
diamonds (Fig. 13):
1. Koh-i-noor, after the second cutting, 106 carats.
2. Loterie d’Angleterre, 49 carats.
3. Nizam of Hyderabad, 279 carats.
4. Orloff, 194 carats.
5. Koh-i-noor, after first cutting, 279 carats.
6. Regent or Pitt, 137 carats.
7. Duke of Tuscany, 133 carats.
8. Star of the South, 124 carats.
9. Pole Star, 40 carats.
10. Tiffany, yellow, 125 carats.
11. Hope, blue diamond, 44 carats.
12. Sancy, 53 carats.
13. Empress Eugenie, 51 carats.
14. Shah, 86 carats.
15. Nassak, 79 carats.
16. Pasha of Egypt, 40 carats.
17. Cullinan, 3025 carats.
18. Excelsior, Jagersfontein, 969 carats.
[Illustration: FIG. 13. SOME HISTORIC DIAMONDS.
To face p. 80.]