|
|
|
|
Gemstone Testing tools @ Jewel Info 4 U
By: Ms Nandita Ray
Tools Required to
Test Gemstones
There is an absolute and definite
need to test gemstones, especially
if they are expensive. Competition,
economics, availability and demand
have all worked towards the
explosion of the gem market. The
markets are flooded with gemstones
of various hues, brand and breed.
Therefore the need to test the
authenticity of gemstones is
imperative. Insurance too has a
hand. They need the gem to be
certified.
In the past, it was pretty easy for
a trained gemologist to distinguish
a flawless gem from a flawed one.
There were no synthetic gems during
those days. Today however, one has
to determine whether a gem is real
or not. Trained eyes cannot always
avoid error, particularly, if the
gem has been manufactured in the
laboratory. It becomes a challenging
task. Earlier on a magnifying glass
was good enough. Presently however,
a host of instruments are used,
especially if one wants to be
absolutely certain of the gem, its
history and pedigree.
It is tricky to test a gemstone.
Some stones are soft, some are
mounted while some can be coated,
treated or easily scratched. One has
to be very careful so as not to
damage the stone in any way. With
technology advancing rapidly, the
tools used for testing are made to
suit ones needs and pockets. Aiding
the tools is a wide range of
database, which lists the particular
characteristics of gems. This is
valuable because the markets are
deluged with zircons or the
synthetic Moissanite, which are look
alike diamonds and very difficult to
differentiate from a real diamond.
Tools required for testing
gemstonesLoupe
Loupe is actually a sophisticated
magnifying glass. It magnifies the
gemstone in detail. The internal
flaws, surface blemishes, cracks and
any other cover ups are easily seen.
It is a powerful convex lens that
produces a magnified image of the
gemstone. The standard loupe that
used is 10X, which magnifies the gem
ten times its size. This standard is
mandatory for testing gemstones in
the USA.
Binocular Microscope
 Binocular Microscope is equipped
to spread light from the bottom and
from the sides. Its function is
similar to the loupe. Presence of
the lights and its superior optical
strength provides excellent clarity.
It usually has 10X magnification
power though 200X can be got. Most
common ones are 10X to 40X. There
are stages of adjusting the iris
diaphragm. It also provides coarse
to fine focusing.
Image courtesy:
www.ottofrei.com
Refractometer
Refractometer measures the
refractive index of the gemstone.
This is needed in order to find out
its composition and physical
properties. It measures the extent
to which the light that passes
through the gemstone from the air is
bent. It helps identify the gem by
comparing the refractive index thus
got with the established values. It
assesses the purity of the gem by
comparing it to the value of a
natural gemstone. It also determines
the amount of solute that has been
added to the gemstone by comparing
the refractive index thus obtained
with the standard curve that is
established. This is done by putting
a drop of a liquid with a high RI,
on a glass disc which is based on
the tip of the Refractometer.
Natural or white light is passed
through this. The RI is reflected in
the magnified gauge.
Dichroscope
Dichroscope is used for the quick
identification of gemstones. It can
effortlessly separate gemstones
based on dichroism, which is the
property of a gemstone to show two
contrasting colors when turned in
two different directions, under a
light. This is used to distinguish
two physically similar looking
gemstones. The dichroscope is used
to view the dissimilar color tones
of the dichroic piece. It can easily
differentiate a Ruby from a
Tourmaline, which is dichroic while
a Ruby is pleochroic. Some gemstones
that are dichroic are Sapphire,
Topaz and Zircon, to name a few.
Polariscope
Polariscope is used to determine
if a gemstone is natural or not. It
can differentiate diamonds from
Moissanite. It also detects strains
in diamonds. It can differentiate
between gems that have double or
single refraction i.e.
birefringence. Double refraction is
the breaking up of a ray of light
into two rays, the ordinary ray and
the extraordinary ray, when it
passes through some materials like
calcite also called Iceland spar.
This effect can take place in gems
that are anisotropic in structure
i.e. having properties that differ
according to the direction of
measurement. The polariscope helps
to track and see the path the rays
of light are taking through the
stone that is being tested. By
measuring the optic characteristics
of transparent to translucent gem
material, the refractive index is
found. Double refractive is only a
property of solids. For transparent
materials, the graph of index,
unlike the wave length, is curved
with a few general characteristics.
A gem is held between two polarized
plates and the light transmitted
through it is studied and based on
the readings the identification is
made.
Some gemstones with double
refraction are Quartz, Tourmaline,
Ruby, Peridot, Sapphire, Zircon and
Rulite to name a few. Diamonds are
isotropic, meaning single
refraction. Topaz, Mica and
Perovskite have triple refraction.
Ultra Violet Light source: - some
gemstones start emitting a
fluorescent glow after being exposed
to short or long ultra violet
radiation. Many gems can be easily
recognized by the Fluorescent color
and the locale. Some fluorescent
minerals are Agrellite, Tugtupite,
dolomite, Fluorite and Benotoite.
Color Filter
Color Filter is also called a
'Chelsea Filter' or 'Emerald
filter'. This instrument helps in
separating natural, synthetic and
imitation gem material. It helps in
establishing whether similar looking
stones exhibiting the same colors
are natural or not. It comes handy
while dealing with some green, red
or blue stones, like blue Spinel and
blue Topaz. It detects dyes in
gemstones also.
Spectroscope
Spectroscope is also used to
separate natural gems from synthetic
gemstones. This is used in
specialized gem testing
laboratories. The differences in the
chemical composition are revealed by
the absorption spectrum of the light
transmitted through the gemstone
that is being tested. The instrument
breaks up the light that is being
transmitted from a gemstone into its
spectral colors. This helps in
testing the various wavelengths that
are being taken in i.e. being
absorbed by the gemstone. This
indicates the type of elements that
are present in the stone, which are
absorbing the wavelengths. It allows
the gemologist to see which color of
light is being absorbed and thus
identify the gemstone.
Specific gravity Liquids
Specific gravity Liquids - this is
important for identifying a number
of gemstones. A carat scale also
called hydrostatic balance is used.
X-Rays
X-Rays are sometimes conducted to
separate natural pearls from
cultured pearls.
Diamond Tester
Diamond Tester is used for
testing diamonds. The unit is
switched on and the diamond that is
to be tested is touched by a pointed
tip. A light will come on to
indicate if the stone is a genuine
diamond or not. It uses thermal
conductivity to differentiate
diamond from its many stimulants.
When the tip is touched to the
diamond, the meter will show green
if it is a real diamond if not then
it will remain in the red zone. This
instrument can be used to test the
minutest diamond, as small as 0.02
carats. It can also separate colored
stones from one another. By merely
touching the thermo electric probe
to the gemstone, the relative heat
conductivity of the material is
exhibited on the dial.
These are the basic instruments.
There are improved and sophisticated
versions of these instruments
available in the markets.
Related Links :
|
 |
Belly Button Piercing
The Egyptians, the Indians and many other cultures pierced this humble button to show the significance of the person sporting a pierced navel - Royalty, Warriors, exceptional Beauty. |
|
|
|
|
|
|
|
