Gem-Stones and Their Distinctive CharactersSmith, George Frederick Herbert
Science
Gem-Stones and Their Distinctive Characters
Smith, George Frederick Herbert
Precious stones
As in the case of diamond, the lapidary judges of the position of the
facet entirely by eye and touch, but a skilled workman can develop
a facet very close to the theoretical position. During recent years
various devices have been invented to enable him to do his work with
greater facility. A machine of this kind is illustrated on Plate IX.
The stone is attached by means of cement to the blunt end, _d_, of
the holder, _b_, which is of the customary kind, while the other end
is inserted in a hole in a wooden piece, _a_, which is adjustable in
height by means of the screw above it. The azimuthal positions of the
facets are arranged by means of the octagonal collar, _c_, the sides
of which are held successively in turn against the guide, _e_. The
stand itself is clamped to the bench. The machine is, however, little
used except for cheap stones, because it is too accurate and leads to
waste of material. Stones are sold by weight, and so long as the eye is
satisfied, no attempt is made to attain to absolute symmetry of shape.
The pictures on Plates X-XIII illustrate lapidaries’ workshops in
various parts of the world. The first two show an office and a workshop
situated in Hatton Garden, London; in the former certain of the staff
are selecting from the parcels stones suitable for cutting. The third
depicts a more primitive establishment at Ekaterinburg in the Urals.
The fourth shows a typical French family—_père_, _mère_, _et fils_—in
the Jura district, all busily engaged; on the table will be noticed a
faceting machine of the kind described above. In the fifth picture a
native lapidary in Calcutta is seen at work with the driving bow in his
right, and the stone in his left, hand.
A curious difference exists in the systems of charging for cutting
diamonds and coloured stones. The cost of cutting the latter is
reckoned by the weight of the finished stone, the rate varying from
1s. to 8s. a carat according to the character of the stone and the
difficulty of the work; while in the case of diamonds, on the other
hand, the weight of the rough material determines the cost, the rate
being about 10s. to 40s. a carat according to the size, which on the
average is equivalent to about 30s. to 120s. a carat calculated on
the weight of the finished stone. The reason of the distinction is
obviously because the proper proportions in a brilliant-cut diamond
must be maintained, whatever be the loss in weight involved; in
coloured stones the shape is not of such primary importance.
[Illustration: _PLATE X_
LAPIDARY’S WORKSHOP AND OFFICE IN ENGLAND]
[Illustration: _PLATE XI_
LAPIDARY’S WORKSHOP IN RUSSIA]
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