Lap′i-da-ry-wheel.
The art of diamond-cutting was probably known in
China and
India at an early day, but the stone was little known among the ancients of
Europe and
Western Asia.
Other varieties of stones were mounted and used in great numbers.
Pliny refers to gem-cutting: “How many hands are worn down that one little joint of our finger may be ornamented.”
The
Arabians brought the diamond into notice.
The discovery of the
Brazilian mines in 1730 made it more common.
Berghen of
Bruges furnished the lapidaries' wheel with diamond-dust, enabling him to cut diamonds, as other stones were cut by the emery previously used.
Diamonds were previously set in the rough.
They are now cut into
brilliants or
rose-diamonds. See brilliant; diamond.
The plano-convex lens of rock-crystal found at Nimroud by
Layard showed the marks of the lapidary's wheel.
The seals of this wonderful nation required the lap to reduce them to form.
They were of various had materials, such as amethyst, agate, etc., gems and semi-gems.
See seal.
The wheels of the lapidary are of two kinds.
The
slicer, which is a thin iron wheel touched with diamond-dust, and used like a circular saw.
The
lap or horizontal wheel, called a
mill, whose flat face is touched with materials of a hardness adapted to the subject and to the stage of the work.
The operations are called
cutting, grinding, or
polishing.
The
mills are known as
slitting, roughing, smoothing, or
polishing.
The materials of the
mills are
iron, lead, tin, willow, mahogany, or of wood covered with
list or
leather.
The abrading materials are
diamond-dust, sapphire, ruby, corundum, emery, rottenstone, etc.
Slicing by a circular saw or
splitting in the lines of natural cleavage are resorted to when admissible.
The
slitting-wheel is usually of
iron touched with
diamond-dust.
The
grinding-wheel is usually of
lead touched with
emery.
The
polishing-wheel of tin touched with rottenstone.
See diamond-cutting.
Fig. 2805 is a view of the lapidary's bench, showing the crank, the driving-wheel, the lap, and the
gim-peg, which latter has holes in which rest the upper end of the
dopp, on which the gem is cemented to be applied to the lap. The choice of holes determines the inclination of the
dopp, and consequently the angle of the facet.
Carnelian, as an example, is first slit with the thin iron slicer, fed with diamond-dust, and moistened with brick oil; secondly, it is rough ground on the lead-mill with coarse emery and water; and thirdly, it is smoothed either on the same lap rubbed down fine, or with a similar lap used with finer emery.
Carnelian, and stones of similar or superior hardness, which are not smaller than about one third of an inch in diameter, are polished on a lead-mill supplied with rottenstone and water.
The face of the polishing-lap is
hacked or
jarred, to enable the powder to adhere.
This
hacking is done by holding a knife in a slanting position, so as to
clatter upon the revolving lap and make small furrows therein, which hold the powder.
Smaller and harder stones are polished on a pewter lap, and still harder upon a copper lap.
Rounded stones, said to be cut
en cabochon, are wrought by means of the
wooden-mill with fine emery, the
list-mill with pumice-stone, and
leather-lap with putty-powder.
Faceted work on pastes and artificial stones, also carnelians, amber, jet, etc., are cut on lead-wheels with emery and polished on pewter with rottenstone.
Gems of a somewhat harder kind use a pewter lap and fine emery for the cutting, and a copper lap with rottenstone for the polishing.
For sapphires, the chrysoberyl, and some few other stones, a copper lap with diamond-powder is used for cutting the facets, and a copper lap with rottenstone for polishing them.
Lastly, for the diamond, two stones are rubbed in a peculiar manner, the one against the other, to start the facets, and they are cut and polished by means of an
iron lap or
skive fed with diamond-powder, being cemented on a
dopp and held upon the
lap by means of a
gim-peg, as above described.
See also diamond-cutting.
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Lapidary's bench. |
Substances treated by the lapidary like carnelian: agate, amethyst, aquamarine, beryl, blood-stone, Brazilian topaz, carbuncle, cat's-eye, chalcedony, chrysolite, chrysoprase, crystal, elvans, emerald, feldspar, flint, fluor-spar, garnet, granite, heliotrope, jade, jaspar, lapis-lazuli, marble, mina nova, onyx, opal, pastes, peridot, plasma, porphyry, quartz, sard, sardonyx, serpentine, topaz.
See Feuchtwanger's “Popular treatise on gems.”
