Testing of Gems Mineral for Identification through Polariscope

June 4, 2022 Dilawer Hussain

Today, we will learn minerals and gem identification through Polariscope. There are thousands of gems, rocks and minerals around the world with different characteristics. Scientists have made an observation based analysis about them using different instruments. In fact, instruments are created for analysis of those observations. Observations are collected, analysed and tested.

Let us first tell you what is Polariscope and what is its purpose? and how the test is done?

What is Polariscope?

A polariscope is an instrument in gemology for testing of gems minerals with single refraction, double refraction, Poly-crystalline material or ADR.

The name of Polar - Scope itself shows or describes that a method to see the gemstones from poles or axis through the Scope. It helps in understanding the different colour of light being transmitted by a gemstone. Polariscope basically is an optical device. A polariscope is composed chiefly of a light source and two crossed polarized lenses such as Polaroid {{Registered Trademark}}. One can determine both the optic character and the optic sign of a gemstone. It helps in understanding synthetic, glass or natural gemstones.

In Polariscope, there are two lenses. One is on the top side called " Analyser". The other part is at the bottom which is called " Polariser". Above Polariser, there is " Tint Plate ". Stone is put on the polarizer and analyse through Analyser. Tint Plate plays role in rotation so gems view can be viewed by 360 degrees.

How to Analyse Gems Mineral through Polariscope:-

There is a brief description of two-phase testing methods by polariscope that how gems are tested.

1st Phase of Test:-

Step:1 Rotate the analyser and check if there is complete darkness

Step: 2 Put gem on the polariser

Step: 3 move the gem or rotate the Tint Plate at 360 degrees and note down the light refraction spectrum on gems.

2nd Phase of Test for Further Confirmation:-

Step:1 Rotate the analyse and check if there is complete darkness

Step: 2 Put gem on the polariser

Step: 3 Leave the gem in full light condition

Step: 4 now quickly rotate the analyser only one time and see the final condition of light on a gem.

Type of Identifications of Gems Mineral through Polariscope

[caption id="attachment_920" align="alignright" width="244"]

Learn about Dichroscope- The Uses[/caption]

Here is the type of results by which we identify gems minerals.

SR ( Single Refraction) / isotropic / Cubic crystalline
DR (Double Refraction) Anisotropic
ADR (Anomalously double refractive or an
Anisotropic Aggregate (Polycrystalline)

1- SR ( Single Refraction) / isotropic / Cubic crystalline

Observations:

Stone remains dark through 360 Degree rotation of Tilt Plate. Single Refractive of Isotropic gemstones gives constant dark light. In 2nd phase test, if gemstone appears bright light, it is SR. It occurs in mostly non-crystalline gemstones.

Conclusions

Isotropic - amorphous or cubic

Examples

garnet, spinels, paste, natural glass, flourite, diamond, opal, plastics

2- DR (Double Refraction) Anisotropic

Observations:

Stone becomes light and dark four times through each 360-degree rotation in most orientation. In double refractive, gems mineral give changing light pattern. Sometimes, it appears as dark and sometimes, it appears as light. This happens with mostly in crystalline gemstones.

Conclusions

Anisotropic - uniaxial or biaxial

Examples

Beryl, Chrysoberyl, Corundum, feldspar, peridot, quartz, topaz, tourmaline, zircon, tanzanite

[embed]https://www.youtube.com/watch?v=mNjCT2lTjS0[/embed]

3-ADR (anomalously double Refractive)

Observations:

Stone shows anomalous extinction effect. In this case, the gemstone gives anomalously double refractive. The pattern of the gems gives snake like dark and light both refraction. Smooth snake like refraction occurs mostly in Synthetic or glass stones.