Dichroscopes by ACMAS Technologies Pvt Ltd.

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DICHROSCOPESMODEL NO.- ACM-D-2602

TECHNOLOGIES PVT. LTD.

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Weiber's Calcite Dichroscope is ideal equipment for research and general applications in the field of testing gems

and stones for being dichroic. Our equipment is helpful in differentiating stones of the same color from one

another. weiber's Dichroscopes can be useful with identifying gemstones that are still in the rough and when

stones are set and difficult to get to with other instruments.

Some gemstones are singly refractive. They exhibit only one colour to observer. There are also gemstones which

exhibit two different colours of light. But most of that is not detected by the human eye since the two colours

produced are so close in wavelength that it becomes difficult for the human eye to identify them. The two colours in

such gemstones mix up to give a slightly different colour. Such stones are called doubly refractive gemstones. For

example, ruby is made up of dark red and light pink colour. But it appears to the viewer as light red.

The property of the gemstone to exhibit two different colours or shades when turned in two different directions

under light is called as dichroism. Examples of the gemstones which are Dichroic are sapphire, zircon, tourmaline

and topaz.

Dichroscope is a tool used to differentiate similar looking

gemstones based on the Dichroic property of the gemstones.

Hence it can easily differentiate gemstones like ruby from

tourmaline since ruby is Dichroic and tourmaline is pleochroic.

Dichroscope also helps to determine Pleochroism and trichorism.

Dichroscope helps to determine the optical properties of a

gemstone.

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Dichroscope is a metal tube which is open on one end and has a lens at the other. It has an optical calcite mounted

inside the tube and produces a double image of the square opening. Enough bright light is directed on a gemstone

and viewed through the dichroscope. Dichroscope separates the different colours of light into its constituent

colours. Light entering the dichroscope is broken into two polarized rays. Two images of different colours indicate

that the vibrations are of different wavelengths and at right angles to each other. If dichroism is not detected in the

first test, the gemstone has to be turned and output colours must be viewed in other directions too.

Pleochroism can be detected by rotating the instrument at an angle of 90 degrees. If the two colours switch sides

on the split image, the gemstone is pleochroic. To determine trichorism, it is necessary to change the orientation of

the stone. If one new colour is determined along with one of the colours of previous orientation, the gemstone

exhibits trichorism. Trichroic gems show three different colours when viewed in three directions perpendicular to

each other. Singly refractive stones produce only one colour on the dichroscope.

Dichroscope works on the principle of plane polarized light. Plane polarized light is the light of a specific

wavelength that is separated from ordinary light and travels in a specific direction. Some waves may travel up and

down and some side to side. When light traveling in different direction is being separated, it is possible to view the

individual colours of specific wavelength.


How does a Dichroscope work

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The calcite dichroscope is made up of a calcite crystal. The calcite has a special characteristic called bi-refringent.

This property of calcite enables the gemstone to appear doubled when looking through it. The calcite crystal splits

the light entering the dichroscope into two rays and thereby helps identify the difference in colours. The two rays

form two images at right angles to each other.

Out of the two dichroscopes, the calcite dichroscope is the most commonly used in the gem testing laboratories to

test the Dichroic property of the gem stones.

Hold the upper portion of the dichroscope near the eye - may be an inch from your eye. Place the gemstone near

the opening. The other end of the dichroscope is hexagonal and hence it is easier to turn the dichroscope while

testing. View the gemstone through the gem view opening. Slowly rotate the dichroscope to complete one full

rotation and observe the colour difference of the two small squares which appear inside the dichroscope while you

rotate. If you observe two colours while you rotate, the gemstone is dichroic. If three colours are observed, the

stone is trichroic. Repeat the observation to confirm the number of colours observed. Observe the strength of the

colours as it helps determine the type of gemstone. Always make sure that sufficient bright light is focused on the

gemstone while you observe the colours using dichroscope. Never use fluorescent light since it can give a false

result.

Calcite Dichroscope

How to use a Dicroscope


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Ÿ Dichroscope helps determine the pleochroic property of the gemstone which helps to separate different types

of gemstones.

Ÿ It also helps to determine whether the gemstone exhibits weak Pleochroism or strong Pleochroism.

Ÿ Dichroscope also helps identify some gemstones.

Ÿ It also helps to study the optical properties of the gemstone

Advantages


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Dichroscopes by ACMAS Technologies Pvt Ltd.

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Transcript of Dichroscopes by ACMAS Technologies Pvt Ltd.