From Wikipedia, the free encyclopedia
Gemstone that has been shaped and polished
A collection of
tourmaline
cabochons in a variety of colours
A
cabochon
(
; from
Middle French
caboche
'head') is a
gemstone
that has been shaped and polished, as opposed to
faceted
. The resulting form is usually a convex (rounded)
obverse
with a flat reverse.
[1]
Cabochon was the default method of preparing gemstones before
gemstone cutting
developed.
[2]
Application
[
edit
]
Cutting
en cabochon
(French: "in the manner of a cabochon") is usually applied to opaque gems, while faceting is usually used for transparent stones. Hardness is also taken into account as softer gemstones with a hardness lower than 7 on the
Mohs hardness scale
are easily scratched, mainly by
silicon dioxide
in dust and grit. This would quickly make translucent gems unattractive?instead they are polished as cabochons, making the scratches less evident.
In asteriated stones such as star
sapphires
and
chatoyant
stones such as cat's eye
chrysoberyl
, a
domed
cabochon cut can show the star or eye, which would not be visible in a faceted cut.
The usual shape for cutting cabochons is an
ellipse
, because the eye is less sensitive to small
asymmetries
in an ellipse, as opposed to in a uniformly round shape, such as a circle, and because the elliptical shape, combined with the dome, is attractive. An exception is cabochons on some
watches' crowns
, which are circular.
The procedure involves cutting a slab of the rough rock with a slab saw, and then stencilling a shape from a template. The slab is then trimmed near the marked line using a
diamond blade
saw?called a trim saw. Diamond-impregnated wheels or
silicon carbide
wheels can be used to grind the rough rock down. Most
lapidary
workshops and production facilities have moved away from silicon carbide to diamond grinding wheels or flat lap disks.
[
citation needed
]
Once the piece is trimmed it can be "dopped" or completed by hand. "Dopping" is normally done by adhering the stone with hard wax onto a length of wooden dowel called a "dop stick". The piece is then ground to the template line, the back edges may be bevelled, and finally the top is sanded and polished to a uniform dome.
Gallery
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References
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External links
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]
Wikimedia Commons has media related to
Cabochons
.
Look up
cabochon
in Wiktionary, the free dictionary.