596 



NA TURE 



[October 12, 1905 



It would have been more conclusive had I been able to 

 get further evidence as to the density and hardness of 

 the crystals ; but 1 am still working at the subject, and 

 hope to add these confirmatory tests. From w-hat I have 

 already said, I think there is no doubt that in these closed 

 vessel explosions we have another method of producing the 

 diamond artificially. 



Sensational as is the story of the diamond industry in 

 South Africa, quite another aspect fi.xes 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 specu- 

 lation. 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, 

 1 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 e.xisted 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." 



Meteoric Diamonds. 



Another diamond theory appeals to the fancy. 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,^ 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." 



-Ucording to this hypothesis, the so-called volcanic pipes 

 are smiply holes bored in the solid earth bv 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 fraa- 

 ments varying in weight from half a ton to a 'fraction of 

 an ounce. There is little doubt these masses formed part 

 of a meteoric shower, although no record exists as to w^lien 

 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. Altooether 

 ten tons of this iron have been collected, and specimens 

 ot the Canyon Diablo meteorite are in most collectors- 

 cabinets. 



An ardent mineralogist— the late Dr. Foot^-cutting a 

 ZTfl; . «h.s meteorite, found the tools were injured bv 

 something vastlv harder than metallic iron. He examined 

 the specimen chemically, and soon after announced to the 

 black and'T ^ ^' the Canyon Diablo meteorite contained 

 black and transparent diamonds. This startling discovery 



"nd \laTZ " T-"^"^ ""' P'-^f" ^^°'^^^" ^"d F"<=dd 

 I ablo me^' T '".^ °" '^^ kilograms of the Canyon 

 d tr^onds ^nTT' ^""^ '^-^^'^y ^°""'^ ^-"""'h black 

 diamonds and transparent diamonds in the form of octa 



"J'*™.""'.'' ^'!f'-.'°g<''her with green h^agonal 

 (Macmillans, 1902.) 



"The nUmond Mines of South Africa." p. 5, 

 ■ C/m,„c<,/A,!,.s, vol. Ixi.,p. =09, iSgo. 



NO. 1876, VOL. 72] 



crystals of carbon silieide. 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. 



I am enabled to show you photographs of true diamonds 

 I myself have extracted from the Canyon Diablo meteorite. 

 .\ fine slab of the meteorite, weighing about seven pounds, 

 is on the table before you. 



Here, then, w'e have incontestable proof of the truth of 

 the meteoric theory. 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 re- 

 moved 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 mav 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 is 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 self-same 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 bv 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. 



Many circumstances point to the conclusion that the 

 diamond of the chemist and the diamond of the mine are 

 strangely akin as to origin. It is evident that the diamond 

 has not been formed 111 situ in the blue ground. The 

 genesis must have taken place at vast 'depths under 

 enormous pressure. The explosion of large diamonds on 

 coming to the surface shows extreme "tension. More 

 diamonds are found in fragments and splinters than in 

 perfect crystals; and it is noteworthy that although these 

 splinters and fragments must be derived from the breaking 

 up of a large crystal, yet in only one instance have pieces 

 been found which could be fi'tted together, and these 

 occurred at different levels. Does not this fact point to the 

 conclusion that the blue ground is not their true matrix '•- 

 Nature does not make fragments of crystals. As the ednes 

 of the crystals are still sharp and unabraded, the lociis'^cf 

 formation cannot have been very distant from the present 

 ^l*?^-. ^""''■'^ ^^'^'■*' probably many sites of crystallisation 

 differing in place and time, or we should n6t see such 

 distinctive characters in the gems from different mines 

 nor, indeed, in the diamonds from different parts of the 

 same mine. 



It is not difficult to imagine that masses of iron saturated 

 with carbon existed formerly at a sufficient depth below 

 the present mines, where temperature and pressure w^ould 

 produce the reactions which laboratory experiments show 

 to be probable. 



Many crystals of diamonds have their surfaces beautifully 

 marked with equilateral triangles, interlaced and of vary- 

 ing sizes. Under the microscope these markings appear 

 as shallow depressions sharply cut out of the surrounding 

 surface; these depressions were supposed bv Gustav Ros^ 

 to indicate the probability that the diamonds at soirr> 



