Polarizing Microscope

A polarizing Microscope is also known as the Polarized Light Microscope. The optical properties of minerals can be determined with the help of a Polarizing Microscope. In order to study minerals under a polarizing microscope, their thin sections of about 0.035 mm thickness are placed on the rotating stage of the microscope and examined.

Main parts of a polarizing microscope:

The main parts of a polarizing microscope are as under;

1. Rotating Stage: A rotating stage is meant to place a thin section of the mineral, which is under study. The mineral slide is placed on this stage. The axis of rotation of the stage coincides with the microscope axis. In modern polarizing microscope, the rotating stage has graduations, which are meant to accurately place the mineral slide.
2. Polarizer: The polarizer transmits polarized light, and is fitted beneath the rotating stage. The polarized light vibrates in the East-West direction.
3. Analyzer: The analyzer is placed in the microscope tube above the stage and is removable. The analyser transmits light vibrating in the north-south. When both the polarizer and analyser are in position, they are said to be crossed.
4. Eyepiece: The eyepiece of the microscope carries cross-hairs, one in the N-S direction and the other in E-W direction. These cross-hairs help in locating a particular mineral grain for detailed examination. They are also useful in aligning cleavage fragments for making angular measurements.
5. Objective: For mineralogical work, generally three objectives are required: (i) low power (2x), (ii) medium (10x), (iii) high power (50x).
6. Iris Diaphragm: This diaphragm is located below the stage. It regulates the intensity of light.
7. Condenser: The condensing lenses are located below the stage. They are used with high power objective and produce converging light rays when required.
8. Bertrand Lens: This lens is used to observe the interference figures.
9. Slot for Accessories: The microscope tube carries a slot at 45° to the cross-hairs. It is used for the insertion of accessory plates.

Examination of Minerals under a Polarizing Microscope

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5. Refractive Index of Minerals
6. Isotropic and An-isotropic minerals
7. Double Refraction of light in minerals 
8. Uni-axial Minerals
9. Bi-axial Minerals
10. Optical Indicatrix of Minerals