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| unmounted
'opalus' |
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| 'opalus'
pendants |
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| opal simulant
'opalus' |
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SYNTHETIC &
IMITATION OPAL |
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Opal
Simulants |
| Opal simulants
have come in a variety of forms. They can
be made by forming colourless non-siliceous
particles into microspheres of the correct
size and allowing them to settle, when diffraction
colours may be obtained. A simulant
using a synthetic resin for this purpose
has been made in Japan. It has the appearance
of a light coloured Coober Pedy opal, and
is very deceptive. If unmounted, however,
it is 'given away' by its low density; it
feels light in weight when held in the hand.
Other techniques have been used in attempts
to simulate the appearance of opal, most
with limited effect. Simple methods such
as mounting crinkled thin foils between
a base and a transparent cabochon have been
used. Another type ('Slocum stone') footnote
incorporates thin reflective film in a glass.
These materials have a transparent appearance,
and the colours are largely produced by
light interference.
Through a magnifying glass the thin individual
flakes of metal, which gives the 'Slocum
stone' its vibrant colours, seem to correspond
with chipboard-like flakes of metal, those
which have been split or broken into smaller
pieces during the manufacturing process.
The appearance of being broken into pieces
is especially noticeable when light passes
through the stone.
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As well as these metallic
flakes, inclusions of gas bubbles and 'schlieren'
are often found, which, by their presence,
help to identify the material.
Gerald Pauley has patented a new type of
simulated
opal called 'Opalus' using computer
graphics and specially designed holograms.
To create the textures and patterns, photographs
were taken of a large number of opal patterns,
colours and textures. These were then scanned
into a computer and amalgamated into complete
random patterns from which simulants where
no two were the same could be made. In the
first instance the colour patterns generated
from the computer were representative of
the base colour of the opal. The hologram
was then applied to give the appearance
of changing colours. The simulated opal
is made in high quality acrylic and can
be mass produced in any shape or size, or
can be made to replicate carvings. In addition,
black opals can be simulated using this
process.
A second Pauley process creates a simulated
opal using holograms and colour interference
layers which allow the colours to appear
through the surface of the product. An unlimited
pattern range simulating those of the natural
opal can be created. |
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