840 
THE TROPICAL AGRICULTURIST. 
[June i, 1891. 
AKTIFICIAL RUBIES. 
A paragraph which will be found in another column 
seems.,to noake it probable that the artificial produc- 
tion of precious stones on a remunerative scale is 
within measurable distance, for MM. Fremy and 
Vernuil are said to have manufactured rubies which, 
for all practical purposes, are as good as the natural 
gems. The two chemists have for many years jiast 
been engaged iu these experiments. But, hitherto, 
the rubies and other crystals which they turned out or 
their retorts, though fine enough to promise better 
things, could not be pronounced quite equal to the 
worst that have been discovered in the Burmese mines. 
In 1878, by heating in a fire-clay crucible a mixture of 
alumina and red lead, MM. Fremy and Verueuil pro- 
duced a vitreous silicate of lead (the silica being derived 
from the crucible), and crystallised alumiua.When to this 
was aided potassium bichromate, the alumina assumed 
the desired that of the ruby. By such a proceis spinels 
it is said, have been turned out almost, if not wholly 
undistinguishable from the natural gems, even after 
tests of a character never likely to be applied to them, 
when worn as orniments, were called into requisition. 
Still, these gems were on a very small scale, aud neither 
hard enough nor endowed with the tint which satisfied 
the expert. But since that date MM. Fremy and 
Verneuil have made remaikable progress, anti, in a 
communication to the French Academy of Sciences, 
intimate that they have at last suocessful'y overcome 
the difficulties which impeded their earlier efforts, and 
are obtaining crystals sufficiently large to be of com- 
nierial value. Some of those already produced are 
being used as ‘‘ jewels,” or pivots, in watches, and are 
affirmed to be in no way inferior to the natural stones. 
The ingtedients differ somewhat from those employed 
twelve years ago. Alumina and a trace of potassium 
bichromate are heated with barium fluoride or a mix- 
ture of fluorides of the alkaline earths, aud a high 
temperature maintained for several da^s. Experience 
has taught that the addition of a small quantity of 
potassium carbonate to this mixture, so as to render the 
mass alkaline, facilitates the formation of the crystals. 
These, it is believed, are produced directly from the 
interaction of the volatile compounds engendered, and, 
by employing crucibles of several litres capacity, in gas 
furnaces, as much as three kilograms, or more 
than six and a-half pounds, of rubies are pro- 
duced at a single operation. Such a mass, even 
admitting that it may not be without flaws aud 
other defects which would render it of little 
value to the lapidary, is larger tbau auy known 
natural stone. Tavernier, the old traveller saw one 
in the Persian Treasury which weighed one hundred 
and seventy-five carats, and the King of Burmah 
possesBod — and perhaps in his exile still po.'^sesses — 
another as large as a pigeon’s egg. The largest iu 
Europe is that presented by Gustavus III. of Sweden 
to the Czarina Catherine. But even this gem does 
not exceed in size a small ben’s egg. 
If, therefore, the chemist is to turn out of his 
alembic rubies six or seven pounds in weight, the 
sooner the holders of the old-sized gems get rid of 
them the better. For, assuredly, no find in Ceylon 
or iu Pegu has ever attained these dimensions. Even 
the gem on which Chardin saw Ihe name of Sheik 
Sephi engraved could not have been a twenliolh 
part as large. Among the accumnlations of the Duke 
of Brunswick sold iu 187G was a Chinese idol cut 
out of a single ruby of immense size, the history of 
the stone, which was part of the loot of the Summer 
Palace ot Pekin, being unknown ; but as the Buddlja 
was sold for six hundred pounds, it could not have 
been of remarkable purity. There are, no doubt, 
tales, more or loss, mythical, of rubies, compared with 
which oven the seven pound concoction of the French 
chemists is not so colossal. Thus, tho one which the 
King ot Ceylon had carried before him at his corona- 
tion oould not have boon mucli less, anil Ibn Batuta 
tells us how he saw, in tho Tsoasury of Aryn Chakra- 
vorti, a Taiiiit Oldof at rnlii.g i’atlam, a ruby bowl 
us Urge as lire p.rlm of one’s hand, while J'Viar 
.JordunuB speaks ot two great rubies belonging to the 
: King of Sylon,” each so big that when grasped it 
projected a finger’s breadth at either side. Sir John 
Maudeville goes even further, for he relates how the 
Emperor of China had in his chamber a pillar of gold 
in which were a ruby and a carbuncle a foot long. If, 
however, a six-pound ruby can be produced, there is no 
scientific reason for believing that the resources of 
chemistry are exhausted at this stage. A twenty or a 
hundred pound one — not, perhaps, of very fine colour, 
but useful for purpotos of art and industry — may be 
the next triumph, and, unquestionably, as the cost is 
not great, some pieces of tfiese large ruby masses may 
be put upon the lapidary’s wheel. MM. Fremy and 
Verneuil are not the first who have essayed this notable 
venture in synthetic chemistry. Indeed, not many 
mouths ago, it w,;S reported that an analyst had succee- 
ded in manufacturing an emerald out of the refuse of 
a gas retort. The ingredients entering into this stone 
are silica, alumina, glucina, magnesia, carbon, and carbo- 
nate of lime, while the intensely green colour for which 
the jewel is valued was said to be due to a slight dash 
of sosquioxide of chromium, though this tint has by 
some authorities been attributed to vegetable matter. 
It may be doubted whether the “gem” so produced was 
anyihing more than a good imitation of an emeiald, so 
far as composition is concerned ; but it was, iuany case, 
iu the line of the research which MM. Eremy and 
Verueuil have puisutd so arduously, and, it seems, 
successful!}'. 
The complexity of the composition of the 
emerald makes close imitation a'most impos- 
sible, and as the tint of many precious stones 
depends entirely upon the presence of a minute 
quantity of a certain chemical in some peculiar com. 
binatiou, all the ingenuity of the experimenter is 
thrown away, so far as the production of a gem capi- 
ble of passing master is concerned. There is, liow- 
ever, no such diificulty in the case of rubies. For this 
stone, like the sapphire, the Oriental topaz, and the 
Oriental amethyst, is crystallised alumina. In the 
ruby the tint is imparted by peroxide of iron — in other 
words by rust — and in tlie sapphire by the protoxide 
of the same metal, the viol t hue being due, perhaps, 
io an admixture of manganese with the iron. The great 
difficulty is so to fuse them, and in snob proporlicus, 
that the results attained during the vast commotion 
of the cartli’s crust may be successfully imitated. More 
than sixty years ago chr} sober} Is were produced by 
subjecting the fluoride of aluminium and gluoinnm 
to a very iiigh temperature, aud early in the century 
Berthier fabricated a great many minerals, including 
chrysolite, augitc, and otliers not of auy economic im- 
portance. Colourless and bine sapphires are among 
the triumphs of the laboratory, and, as far Lack as 
1837, Gaudiu produced the ruby on a small scale by 
exposing aluminium to the heat of the oxy-hydrogen 
blowpipe, and thus obtaining fused alumina, which 
is readily coloured by the addition of oxide of otirominm. 
The resultant crystals were iu the rhombohedrals 
characteristic of the mineral, and, it is said, had equal 
hardness an specific gravity. Euelmen arrived at much 
the same end by dissolving alumina in boric acid, at a 
high temperature, and on the cooling of the liquid ob- 
tained the alumina in a crystallised form, which, with 
tho addition of chromate of ammonia, became, to all 
intents aud purposes, rubies. Again — and this by no 
means exhausts the roll of experiments — Sainte-Claire, 
Ueville, and Caron, by heating fluoride ot aluminium, 
fluoride of chromium, and boric acid, obtained fluoride 
of boron, which, escaping iu a volatile condition, left 
a residuum of solid alumina coloured by the chrome. 
When the mincriil is simpler the chances of success 
are greater. Thus, the diamond bidng known to be 
pure carbon, it is a questkn of time for it to be exactly 
imitated by the crystallisation of that element. This, 
it may be remembered, Mr. Han'iay actually succeeded 
i'j accomplishing ten or eleven years ago, though the 
cost was BO great, aud the result so valueless commer- 
cially, that the experiments have not been continued 
.Still, the principle ouce discovered, the rest will follow. 
For a long time to come the artificial gems will be in- 
ferior to the natural ones, Nature has worked on so 
large a scale, aud with such gigantic appllauces, that 
the puny tools of the chemist can be ot no avail. 
