polariscope

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PRODUCT OVERVIEW

Weiber polariscopes are used to swiftly, accurately check if gemstones are single or double refracting, in a simple way. Our equipment is very useful in identifying Moissanite and detecting strain in diamonds and other gems. This equipment of ours is also used to separate synthetic amethyst from genuine. This desktop instrument has a built in light source.

DETAILLED TECHNICAL EXPLANATION

Polariscope is an instrument used in gemology which helps to find if the gemstone is single refractive or double refractive and also allows determining the various crystal axis of the stone.

A Polariscope is used to determine whether the gemstone is natural or synthetic.

This is one of the most commonly used instruments by the gemmologists. The use of plane polarized light allows us to see the actual path the beams are taking through the stone.

A polariscope is made of two Polaroid plates that rotate, a power switch, a stone holder and a bottom light source. Two polarized filters or plates are made of polarizing plastic sheets, one is on the top of the instrument, known as analyzer and the other is on the bottom of the instrument, known as polarizer. Polarizer and analyzer have their own vibrational planes. When the vibrational plane of polarizer and the vibrational direction of the analyzer are at right angles to each other, the field between them appears dark. This position is known as crossed position and it is in this position that the gemstones are tested to see if they are isotropic, anisotropic, anomalously double refractive and anisotropic aggregate. The polariscope can be used to determine the optical character as well as the optical sign of the gemstone.

Polariscope can also be used to determine the strains in diamond. It helps in separating natural gemstones from synthetic ones and also helps to distinguish solid inclusions from negative inclusions. Polariscope can also be used for recognizing polysynthetic twinning.

POLARISCOPES

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How to use a Polariscope

How to use a Polariscope?

• The polariscope is adjusted for cross position by setting the vibrational plane of polarizer and the vibrational direction of analyzer at right angles to each other.

• Turn on the light source and place the gemstone on the rotating platform above the polarizer. The gemstone is rotated in a vertical axis.

• O b s e r v e t h e g e m s t o n e t h r o u g h t h e analyzer and note down the observations

• Based on the observations the nature of the gemstone can be determined as follows.

• If the stone remains dark throughout the 360 degree rotation, the stone is said to be isotropic or singly refractive.

• If the stone darkens evenly at every 90 degree interval, the stone is said to be doubly refractive or anisotropic.

• If the stone appears light throughout the rotation, it is said to be microcrystalline or crypto crystalline aggregate.

• If the stone shows anomalous double refraction, the stone is singly refractive. Anomalous double refraction may be confusing at times. Hence when there is a suspicion that about anomalous double refraction, it is recommended to orientate the stone in the position where it appears lightest. Then turn the analyzer to 90 degree. If the stone appears lighter than before it is said to exhibit anomalous double refraction and hence is singly refractive. If the stone appears the same, it is doubly refractive.


POLARISCOPES


Technical Specifications

• Power input : 110V ~ 220 V 50 HZ• Storage Temperature : 10 - 35 °C

How does a Polariscope work?

Polariscope works on the principle of plane polarized

light. Single refractive gemstones do not break the

plane polarized light into various colours. There is

only one beam of light coming out. Examples of singly

refractive gemstones include diamonds. Double

refractive gemstones break the plane polarized light

into two paths. One is the ordinary beam and the

other is the extraordinary beam. Based on analyzing

the transmitted light, the nature of gemstone can be

identified. Some of the doubly refractive gemstones

are quartz, tourmaline, ruby, zircon, peridot, sapphire

and rulite.

Both the filters i.e. polarizer and the analyzer are

turned to the dark position. When plane polarized

light is passed through the gemstone, the singly

refractive stone remains dark since it does not change

the path of light. Hence it remains dark when

observed in all positions. But in case of double

refractive gemstone, when plane polarized light is

passed through it, the stone changes the path of the

light and hence the direction of the light wave

changes. This produces light that is no more

polarized. The change in direction of light makes the

stone change from light to dark as it is rotated

between the Polaroid plates.

Since the polariscope works through plane polarized

light, it can be used to test transparent as well as

translucent gemstones, but cannot be used to test

opaque materials. Once the stone is found to be

doubly refractive, a conoscope can help to determine

the optic interference figure. Optic interference figure

helps to locate the various directions in which the light

is traveling through the stone. This information in turn

helps to identify the type of gemstone. The different

shadow patterns observed through the polariscope

helps to determine the crystal structure and

diagnostic patterns of the gemstone.


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polariscope

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