METEORIC DIAMONDS
Sensational as is the story of the diamond industry in South
Africa, quite another aspect fixes the attention of the chemist.
The diamonds come out of the mines, but how did they get in? How
were they formed? What is their origin?
Gardner Williams, who knows more about diamonds than any man
living, is little inclined to indulge in speculation. In his
fascinating book he frankly says:
“I have been frequently asked, ‘What is your theory of the original
crystallisation of the diamond?’ and the answer has always been, ‘I
have none; for after seventeen years of thoughtful study, coupled
with practical research, I find that it is easier to “drive a coach
and four” through most theories that have been propounded than to
suggest one which would be based on any non-assailable data.’
All that can be said is that in some unknown manner carbon, which
existed deep down in the internal regions of the earth, was changed
from its black and uninviting appearance to the most beautiful gem
which ever saw the light of day.”
Another diamond theory appeals to the imagination. It is said
the diamond is a gift from Heaven, conveyed to earth in meteoric
showers. The suggestion, I believe, was first broached by A.
Meydenbauer,[12] who says, “The diamond can only be of cosmic
origin, having fallen as a meteorite at later periods of the
earth’s formation. The available localities of the diamond contain
the residues of not very compact meteoric masses which may,
perhaps, have fallen in prehistoric ages, and which have penetrated
more or less deeply, according to the more or less resistant
character of the surface where they fell. Their remains are
crumbling away on exposure to the air and sun, and the rain has
long ago washed away all prominent masses. The enclosed diamonds
have remained scattered in the river beds, while the fine light
matrix has been swept away.”
According to this hypothesis, the so-called volcanic pipes are
simply holes bored in the solid earth by the impact of monstrous
meteors--the larger masses boring the holes, while the smaller
masses, disintegrating in their fall, distributed diamonds
broadcast. Bizarre as such a theory appears, I am bound to say
there are many circumstances which show that the notion of the
heavens raining diamonds is not impossible.
The most striking confirmation of the meteoric theory comes from
Arizona. Here, on a broad open plain, over an area about five
miles in diameter, have been scattered one or two thousand masses
of metallic iron, the fragments varying in weight from half a ton
to a fraction of an ounce. There is no doubt these masses formed
part of a meteoric shower, although no record exists as to when
the fall took place. Curiously enough, near the centre, where most
of the meteorites have been found, is a crater with raised edges
three-quarters of a mile in diameter and about 600 feet deep,
bearing exactly the appearance which would be produced had a mighty
mass of iron struck the ground and buried itself deep under the
surface. Altogether, ten tons of this iron have been collected, and
specimens of the Canyon Diablo meteorite are in most collectors’
cabinets.
An ardent mineralogist--the late Dr. Foote--cutting a section of
this meteorite, found the tools were injured by something vastly
harder than metallic iron. He examined the specimen chemically,
and soon after announced to the scientific world that the Canyon
Diablo meteorite contained black and transparent diamonds. This
startling discovery was afterwards verified by Professors Moissan
and Friedel, and Moissan, working on 183 kilogrammes of the Canyon
Diablo meteorite, has recently found smooth black diamonds and
transparent diamonds in the form of octahedra with rounded edges,
together with green, hexagonal crystals of carbon silicide. The
presence of carbon silicide in the meteorite shows that it must at
some time have experienced the temperature of the electric furnace.
Since this revelation the search for diamonds in meteorites has
occupied the attention of chemists all over the world.
Fig. 23 A, C, and D, are reproductions of photographs of true
diamonds I myself have extracted from the Canyon Diablo meteorite.
[Illustration: FIG. 23. DIAMONDS FROM CANYON DIABLO METEORITE.
To face p. 138.]
Under atmospheric influences the iron would rapidly oxidise and
rust away, colouring the adjacent soil with red oxide of iron.
The meteoric diamonds would be unaffected and left on the surface
of the soil, to be found haphazard when oxidation had removed the
last proof of their celestial origin. That there are still lumps of
iron left at Arizona is merely due to the extreme dryness of the
climate and the comparatively short time that the iron has been on
our planet. We are here witnesses to the course of an event which
may have happened in geologic times anywhere on the earth’s surface.
Although in Arizona diamonds have fallen from the skies,
confounding our senses, this descent of precious stones is what may
be called a freak of nature rather than a normal occurrence. To
the modern student of science there is no great difference between
the composition of our earth and that of extra-terrestrial masses.
The mineral peridot is a constant extra-terrestrial visitor,
present in most meteorites. And yet no one doubts that peridot
is also a true constituent of rocks formed on this earth. The
spectroscope reveals that the elementary composition of the stars
and the earth are pretty much the same; and the spectroscope also
shows that meteorites have as much of earth as of heaven in their
composition. Indeed, not only are the selfsame elements present in
meteorites, but they are combined in the same way to form the same
minerals as in the crust of the earth.
It is certain from observations I have made, corroborated
by experience gained in the laboratory, that iron at a high
temperature and under great pressure--conditions existent at great
depths below the surface of the earth--acts as the long-sought
solvent for carbon, and will allow it to crystallise out in the
form of diamond. But it is also certain, from the evidence afforded
by the Arizona and other meteorites, that similar conditions have
existed among bodies in space, and that on more than one occasion a
meteorite freighted with jewels has fallen as a star from the sky.
INDEX
Able, Sir F., closed vessel experiments, 122
Absorption spectrum of diamond, 101
Aliwal North, 6
Alluvial deposits of diamonds, 9
Amygdaloidal trap, 10
Arizona meteor, 136
Arkansas, diamonds in, 2
Ash of diamond, 82, 89
Augite, 20
Automatic diamond collector, 56
Barytes, 71
-- density of, 93
Basalt, 15
Basutos, 12, 39
Bechuanas, 12, 39
Beryl, density of, 93
-- refractive index of, 103
Biotite, 20
Blackening of diamonds, 98
Blue ground, 10, 47
-- -- diamantiferous, 18, 19
Boart, 81,
-- combustion temperature of, 90
-- density of, 93
Boiling-point of carbon, 110
Bonney, Rev. Professor, 67
Boyle on the diamond, 100
Brazil, diamonds in, 4
Breakwater, Cape Town, 36
Breccia, diamantiferous, 19
Brilliant cut diamond, 102
British Association in South Africa, 7
British Guiana, diamonds in, 4
Bronzite, 20, 71
-- hydrated, 19
Bultfontein Mine, 14
-- -- characteristics of diamond from, 64
Bursting of diamonds, 105
Calcite, 20, 97
California, diamonds in, 3
Canada balsam, refractive index of, 103
Canyon Diablo meteorite, 136
Cape Colony, 5
Cape Town, 5
Carat, equivalent in grains, 69
Carbon, boiling and melting point of, 110
-- combustion temperature of, 90
-- critical point of, 110
-- density of, 93
-- dissolved in iron, 116
-- volatilisation of, 115
Carbonado, 81
-- density of, 93
Characteristics of diamonds from the different mines, 64
Chemical properties of diamond, 89
Chromate of lead, refractive index of, 103
Chrome diopside, 71
-- iron, 20
-- -- ore, 71
-- -- -- density of, 93
Chromite, 20
Classification of rough diamonds, 73
Cleavage of diamonds, 78
Coke, density of, 93
Colesberg Kopje, 26
Collecting the gems, 55
Coloured diamonds, 62, 82
Combustion of diamond, 89
-- temperatures of diamond, boart, graphite, and carbon, 90
“Comet” crushers, 49
Compound system, 36, 37
Concentrating and washing machinery, 49
Convict labourers, 71
Cordite, diamond from explosion of, 123
Corundum, 20
-- density of, 93
Cradock, 6
Craters or pipes, 18
Crown glass, refractive index of, 103
Crusher, “Comet,” 49
Crystallisation of diamond, 86
Crystals, octahedra, of diamond, 63, 86
Cullinan diamond, 15, 76, 80, 104
Dallas, Captain, 40
De Beers Consolidated Mines, 7, 33
-- -- floors at Kenilworth, 47
-- -- Mine, 14, 24, 34
-- -- -- characteristics of diamonds from, 64
-- -- strong-room, 74
Delhi diamond, 107
Density of diamond, 57, 93
-- of graphite, 83, 93
-- of stones accompanying diamond, 70, 71, 93, 95
Depositing floors, 46
Dewar, Sir J., conversion of diamond into graphite, 123
Diabase, olivine, 16
Diallage, 20
Diamond, absorption spectrum of, 101
-- and polarised light, 104
-- a new formation of, 122
-- ash of, 82, 89
-- collector, automatic, 56
-- combustion of, 89
-- -- temperature of, 90
-- converted into graphite, 100
-- density of, 57, 93
-- etched by burning, 88
-- explosion of, 120
-- genesis of the, 115
-- in meteors, 134
-- in Röntgen rays, 107
-- matrix of, 67
-- natural formation of, 127
-- Office at Kimberley, 73
-- physical and chemical properties of, 89
-- pipes or craters, 18
-- radio-activity of, 109
-- refractive index of, 103
-- Trade Act, 36
-- triangular markings on, 87
-- tribo-luminescence of, 100
Diamonds, coloured or fancy, 62, 82
-- Maskelyne on, 1
-- noteworthy, 76
-- phosphorescence of, 96
-- produced, weight, value of, 35
-- yield of, from De Beers, 60
Drift, diamonds from the, 12
Duke of Tuscany diamond, 80
Dutch boart, or zircon, 59
Dutoitspan Mine, 14, 23
-- -- characteristics of diamonds from, 64
Eclogite, 20
-- containing diamonds, 67
Electrons, bombardment by, 98
Emerald, refractive index of, 103
Empress Eugenie diamond, 80
Enstatite, 20
Explosion of diamonds, 120
Excelsior diamond, 80
Fancy stones, 62
Fingoes, 39
Flint glass, refractive index of, 103
“Floating Reef,” 21
Floors, depositing, 46
Fluor-spar, refractive index of, 103
Formation, new, of diamond, 122
Fort Beaufort, 6
Franklinite, 97
Frank Smith Mine, 15
-- -- -- characteristics of diamonds from, 66
Fraserburg, 6
Garnet, 20, 70
-- density of, 93
Genesis of the diamond, 115
“Golden fancies,” 65
Granite, 18
-- density of, 93
Graphite, 81, 83
-- combustion temperature of, 90
-- conversion of diamond into, 100
-- density of, 93
-- diamonds coated with, 99
Graphitic oxide, 83, 93
Grease, collecting diamonds by aid of, 57
Hard blue ground, 47
Hardness of diamond, 90
Haulage system, 46
Hexakis-octahedron crystal, 86
Hope blue diamond, the, 80
Hornblende, 71
-- density of, 93
Iceland spar, refractive index of, 103
Ice, refractive index of, 103
I.D.B. laws (Illicit Diamond Buying), 36
Ilmenite, 20
India, diamonds in, 4
Inverel diamonds, 91
Internal strain in diamonds, 104
Iron a solvent for carbon, 116
-- ore, density of, 93
-- pyrites, 20
Jagersfontein diamond, 79
-- Mine, 14
-- -- characteristics of diamonds from, 68
Jeffreysite, 20
Kafirs, 42
Kamfersdam Mine, 15
-- -- characteristics of diamonds from, 66
Kenilworth depositing floors, 47
Kimberley, 6
-- blue ground, 10
-- mines, 14, 23, 34
-- Mine in old days, 25
-- -- at the present day, 34
-- -- characteristics of diamonds from, 63
-- shales, 15
-- West Mine, 15
-- -- -- characteristics of diamonds from, 66
Kirsten’s automatic diamond collector, 57
Klipdam, 8, 23
Koffyfontein Mine, 14
Koh-i-noor diamond, 80
-- hardness of, 91
Kyanite, 20, 71
Lamp, ultra-violet, 97
Leicester Mine, 15, 23
-- -- characteristics of diamonds from, 67
Loterie d’Angleterre diamond, 80
Lustre of rough diamonds, 56
Machinery for washing and concentrating, 49
Macles, 86
Magnetite, 20, 71
-- density of, 93
Maskelyne on diamonds, 1
Matabele, 12, 39
Matrix of diamond, 67
Melaphyre, 10, 16
Melting-point of carbon, 110
Meteor, Canyon Diablo, 136
Meteoric diamonds, 134
Meydenbauer on meteoric diamonds, 135
Mica, 20, 71
-- density of, 93
Moissan’s experiments on the genesis of diamond, 115
Mud volcano, 24
Nassak diamond, 80
Natal, coal in, 6
Natural formation of diamond, 127
Newlands Mine, 15
-- -- characteristics of diamonds from, 67
New Rush diggings, 26
Nizam of Hyderabad diamond, 80
Noble, Sir A., experiments, 122, 131
Noteworthy diamonds, 76
Octahedral crystals of diamond, 63, 86
Olivine, 20
-- diabase, 16
Orange River Colony, coal in, 6
-- -- -- diamonds in, 14
Orloff diamond, 80
Pasha of Egypt diamond, 80
Paterson, Mr., description of Kimberley in old days, 25
Peridot, 20, 139
Peridotite, 3
Perofskite, 20
Phosphorescence of diamonds, 96
Phosphorus, refractive index of, 103
Physical properties of diamond, 89
Picking tables, 51
Pipes or craters, 18
Pitt diamond, 80
Polarised light and diamond, 104
Pole Star diamond, 80
Pondos, 39, 42
Premier Mine, 15, 76
Prodigious diamonds, 76
Pseudobrookite, 20
Pulsator, 52
Pyrope, 70
Quartzite, 16, 20
-- density of, 93
-- refractive index of, 103
Radio-activity of diamond, 109
Radium, action on diamond, 108
“Reef,” 21
Refractive indices, 103
Refractivity of diamond, 102
Regent diamond, 80
Reunert, Mr., description of Kimberley Mine, 30
Rhodes, Cecil John, 34
River washings, 7
Rock shafts, 43
Röntgen rays, diamond in, 107
Ruby, refractive index of, 103
Rutile, 20
Sahlite, 20
Sancy diamond, 80
Savings of the native workmen, 41
Scalenohedron diamond crystal, 86
Serpentine, 19
Shafts, rock, 43
Shah diamond, 80
Shales, Kimberley, 15
Shangains, 39
Shells in blue ground, 21
Shot boart, 81
Silver and thallium, nitrate of, 94
Smaragdite, 20
Soft blue ground, 47
Sorting the diamantiferous gravel, 55
Specific gravity, _see_ Density
Spectrum, absorption of diamond, 101
Sphalerite, 100
Spinthariscope, 108
Sprat’s _History of the Royal Society_, 1
Sprouting graphite, 84
Star of the South diamond, 80
Stones other than diamonds, 70, 71, 93, 95
Strain, internal, in diamonds, 104
Sulphur, refractive index of, 103
Swazis, 39
Ultra-violet lamp to show phosphorescence, 97
Underground workings, 43
United States, diamonds in, 2
Vaalite, 20
Vaal River, 8, 16
Valuators, 73
Value of diamonds per carat, 12, 69
Value of diamonds, progressive increase in, 69
Vermiculite, 20
Volatilisation of carbon, 115
Volcanic necks, 18
Volcano, mud, 24
Wages, scale of, 35
Washing and concentrating machinery, 49
Wesselton Mine, 14, 15, 23, 35
-- -- characteristics of diamonds from, 65
Willemite, 97
Wollastonite, 20
Workings, underground, 43
Yellow ground, diamantiferous, 19
Yield of diamonds, annual, 60
-- -- -- total, 35
-- falls off with depth, 68
-- per load of blue ground, 62
Zimbabwe ruins, 40
Zircon, 20, 59, 71
-- density of, 93
Zulus, 12, 39, 40
W. BRENDON AND SON, LTD., PRINTERS, PLYMOUTH
FOOTNOTES:
[1] _Chemical News_, Vol. I, p. 208.
[2] Mr. Paterson called “limey stuff” what is now termed “blue
ground.” It was also formerly called “marl stuff,” “blue stuff,”
and “blue clay.”
[3] The original name for the Kimberley Mine. It was also sometimes
known as “Colesberg Kopje.”
[4] _Diamonds and Gold in South Africa._ By T. Reunert.
Johannesburg, 1893.
[5] According to Gardner Williams the South African carat is
equivalent to 3·174 grains. In Latimer Clark’s _Dictionary of
Metric and other Useful Measures_ the diamond carat is given as
equal to 3·1683 grains = 0·2053 gramme = 4 diamond grains; 1
diamond grain = 0·792 troy grain; 151·5 diamond carats = 1 ounce
troy.
Webster’s _International Dictionary_ gives the diamond carat as
equal to 3⅕ troy grains.
_The Oxford English Dictionary_ says the carat was originally 1/144
of an ounce, or 3⅓ grains, but now equal to about 3⅕ grains, though
varying slightly with time and place.
The _Century Dictionary_ says the diamond carat is equal to about
3⅙ troy grains, and adds that in 1877 the weight of the carat was
fixed by a syndicate of London, Paris, and Amsterdam jewellers at
205 milligrammes. This would make the carat equal to 3·163 troy
grains. A law has been passed in France ordaining that in the
purchase or sale of diamonds and other precious stones the term
“metric carat” shall be employed to designate a weight of 200
milligrammes (3·086 grains troy), and prohibiting the use of the
word carat to designate any other weight.
[6] Artificial tribo-luminescent sphalerite:--
Zinc carbonate 100 parts
Flower of sulphur 30 ”
Manganese sulphate ½ per cent.
Mix with distilled water and dry at a gentle heat. Put in luted
crucible and keep at a bright red heat for from two to three hours.
[7] Sir James Dewar, in a Friday evening discourse at the Royal
Institution in 1880, showed an experiment proving that the
temperature of the interior of a carbon tube heated by an outside
electric arc was higher than that of the oxy-hydrogen flame. He
placed a few small crystals of diamond in the carbon tube, and,
maintaining a current of hydrogen to prevent oxidation, raised the
temperature of the tube in an electric furnace to that of the arc.
In a few minutes the diamond was transformed into graphite. At
first sight this would seem to show that diamond cannot be formed
at temperatures above that of the arc. It is probable, however, for
reasons given above, that at exceedingly high pressures the result
would be different.
[8] The silica was in the form of spheres, perfectly shaped and
transparent, mostly colourless, but among them several of a ruby
colour. When 5 per cent of silica was added to cordite, the residue
of the closed vessel explosion contained a much larger quantity of
these spheres.
[9] A pressure of fifteen tons on the square inch would exist not
many miles beneath the surface of the earth.
[10] There are abundant signs that a considerable portion of this
part of Africa was once under water, and a fresh-water shell has
been found in apparently undisturbed blue ground at Kimberley.
[11] The water sunk in wells close to the Kimberley mine is
sometimes impregnated with paraffin, and Sir H. Roscoe extracted a
solid hydrocarbon from the “blue ground.”
[12] _Chemical News_, vol. lxi, p. 209, 1890.
TRANSCRIBER’S NOTE
Obvious typographical errors and punctuation errors have been
corrected after careful comparison with other occurrences within
the text and consultation of external sources.
All misspellings in the text, and inconsistent or archaic usage,
have been retained: for example, unfrequent; clayey; friable;
slaty; imbed; stoped; peculation; situate.
In the Table of Contents, the Index page number ‘145’ has been
replaced by ‘141’.
In the Index, ‘Colesberg Copje’ has been replaced by
‘Colesberg Kopje’, and ‘DeBeers’ has been replaced by
‘De Beers’.