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Jewellers Loupe @ Jewel Info 4 U
By: Ritika Changrani
Summary: A jeweller's loupe
is a tool that helps identify the
internal flaws, cracks and blemishes
on the surface and any other cover
ups on the gemstone.
A Loupe is just a magnifying glass.
It helps to see the magnified image
of gemstone and serves as the
identification and grading tool. A
Loupe is made of a powerful
convex
lens. Through a jeweller's loupe,
one can easily see the internal
flaws, cracks and blemishes on the
surface and any other cover ups on
the gemstone. Jeweller's loupe is
the most important test equipment
for testing gemstones.
How to Choose a Jeweller's Loupe?
There are two important factors to
be considered while choosing the
right jeweller's loupe. They are the
size and magnification of the lens
and the optical quality. Loupes are
available in different sizes and
powers. The standard size used for
testing gemstones is of 18mm length
with 10X, which magnifies the
gemstone to ten times its size. The
jeweller's loupe is available in 20X
and 30X, but they are not much used.
 The jeweller's loupe has to be
tested for achromatic and spherical
aberrations. Chromatic aberration
refers to colour fringes of the
image due to dispersion caused
inside the glass lens. The loupes
which are corrected from chromatic
aberration are known as achromatic.
Spherical aberration refers to the
distortion caused due to the
differences in refraction on the
outer edges of the lens and the rays
traveling through the center. The
loupes which are corrected for
spherical aberration are termed as
'aplanatic'.
While choosing a jeweller's loupe it
is necessary to check that they are
achromatic and aplanatic to get
accurate results. In a better
quality jeweller's loupe, three
lenses (known as triplet loupe) are
used so that the field of vision is
in focus to the edges and no false
colour is imparted to the eye. The
use of three lenses eliminates the
pin cushion distortions and
chromatic and spherical aberrations.
While selecting a jeweller's loupe
you can easily identify if they are
achromatic and aplanatic. Look at
the white light through the loupe.
If the white light remains white
without changing the colour, the
lens is corrected for chromatic
aberration. Similarly spherical
aberration can be tested by looking
at the mm squared drawing paper. If
they remain squares when looking
through the loupe, the loupe is
aplanatic.
It is also better to choose a loupe
with black framing around the lens,
since this avoids reflections which
may alter the color of the object
under view. Do not opt for golden or
other bright coloured frames since
they interfere with the colours.
How Does a Jeweller's Loupe Work?
Jeweller's Loupe magnifies the image
of the stone under test as per its
magnification power. Suppose, we are
using a 10x loupe, the image is
magnified to ten times its original
size. This helps us clearly see the
flaws, cracks and other distortions
in the stone. A triplet loupe
consists of one 'plano-convex lens',
one bi-concave lens and one
bi-convex lens. The 'plano-convex
lens' is used to eliminate spherical
aberration and the other two are
used to eliminate chromatic
aberration. Depending on the
observations, the nature of the
gemstone can be detected. Jeweller's
loupe helps to detect diamonds,
sapphire, alexandrite,
ruby, pearls
and many other gems.
How to Use a Jeweller's Loupe
- Remove your spectacles if you are
wearing one. Unfold the jeweller's
loupe.
- Hold the jeweller's loupe between
the thumb and the index finger. Keep
the jeweller's loupe as close to the
eye as possible without touching the
eyeball. The loupe should be so
close that your eyelashes almost
brush through it. Once the loupe is
close to your eye, see that it is
kept stationary by letting the back
of the thumb rest against the side
of the nose. Keep the remaining
three fingers in parallel or just
below the index finger. Keep both
your eyes open to avoid eye
straining.
- Make sure there's enough light in
the place where you are observing
the gemstone. Fluorescent and other
light bulbs lack some colours which
are necessary. Hence sunlight is the
best light for the testing gemstone.
Diamond lamps can also be used.
- Place a clean white soft cloth on
the surface you are using. This
helps to avoid scratches on the
gemstone and also avoids rolling
down in case it slips down. Next,
place the stone at a distance of an
inch or a little more on the other
side of the gem loupe. Peering
through the gem loupe, move the
stone to and fro until it comes in
focus. Keep moving the stone front
and back and turn the stone in
different directions until the area
of the stone is seen with sharp
focus.
- Note the external and internal
features of gemstones. Look if there
is unevenness in colour. If there is
unevenness in colour, there is a
possibility that the gemstone is
dyed or painted to imitate a high
quality gem. Many deceptions which
cannot appear to the naked eye can
be observed through the jeweller's
loupe. If you already have some real
gems of similar types, you can
observe both and compare them.
- Some of the things you should
observe while testing the gemstone
through the loupe are :
-
Symmetry: Check if the gemstone
has a balanced symmetry
-
Number of facets: Observe whether
the gemstone has the right number of
facets required for the particular
cut
- Sharpness of the facet edges: Hard
stones have sharp edges while
synthetic stones have soft edges
- Inclusions, flaws and bubbles in
gemstones: Inclusions, if present,
don't necessarily indicate that the
gemstone is bad. Instead, the
gemstone can be a natural gem. Flaws
in gemstones are not an indication
that the gemstone is of low value.
Bubbles in gemstone indicate that
the gemstone is synthetic.
- Scratches and cracks in gemstone:
Soft stones tend to scratch easily
while hard stones crack.
To buy Jewellers Loupe
National Jewelry Supplies
Jewellers Tools
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