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How much do you know about gem polariscope?

 

A gemstone polariscope is a simple and easy to operate gemstone identification instrument, mainly used to detect the optical properties of gemstones. It can also be used to determine the axial orientation of gemstones and check their polychromism.

Figure 1 Structure of a Gem polariscope

 

  1. The structure of gemstone polariscope

 

  1. Light source: When using a gemstone polariscope, itneeds to with light source, and light source should be turned onwhile using;
  2. Lower filter: it is alight filtering devicewhich can filter natural light into polarized light;
  3. Object Stage: whenusing a gemstone polariscope, need placing the gemstones on this object stage which can rotate 360 ° horizontally;
  4. Top filter: it is a light filterwhichcan rotate 360 ° horizontally to filter polarized light into orthogonal polarized light;
  5. Conoscope:we can use it to observe the axial properties of heterogeneous gemstones;
  6. Power button: it is for controlling the on and off of the light source.

 

  1. The main functions of gemstone polariscope

 

Determine the optical characteristics of gemstones.

 

Adjust the gemstone polariscope to orthogonal polarized light, then place the gemstone on the object stage, rotate the object stage 360 °, and judge the optical characteristics of the gemstone through observation of phenomena and interference patterns. The optical characteristics of the gemstone can be divided into the following 5 situations.

 

 

No. appearance interference patterns optical characteristics
1 All dark(Figure 1) No homogeneous
2 Abnormal extinction(Figure 3) No
3 All bright(Figure 4) No nonhomogeneous aggregation
4 Four”bright”and four”dark”(Figure 5) uniaxial crystal interference figure(Figure 6) nonhomogeneous uniaxial crystal
5 Four”bright”and four”dark”(Figure 5) biaxial crystal  interference figure(Figure 7) biaxial crystal

     

 

Figure 5 Turn 360°,Four”bright”and four”dark”

(Bright degrees:45°、135°、225°315°,Dark degrees:0°、90°、180°、270°)

Figure 6  uniaxial crystal interference figure

Figure 7  biaxial crystal interference figure

 

  1. Which gemstones cannot use a polariscope to detect

 

  1. Opaque gemstones are not suitable for gemstone polariscope;
  2. Gemstone size smaller than 1mm are not suitable for gemstone polariscope;
  3. Gems with a large number of cracks and inclusions are not suitable for gemstone polariscope.

 

  1. Precautions for using gemstone polarizers

 

  1. When testing faceted gemstones, it is best to let the faceted surface of the pavilion come into contact with the object stage;
  2. When abnormal extinction occurs, please use a dichroscope or refractometer for verification;
  3. Only heterogeneous single crystal can be used to determine the axiality of gemstones using an interference ball;
  4. During the test, if you encounter any abnormal situation, please change the direction of the gemstone and test again.

 

  1. Common faults and solutions for gem polariscope

 

  1. The light source can not be turned on: Check whether the power supply is plugged in tightly. If not, please plug in the power supply tightly and try again. If it is still can not be turned on after being plugged in tightly, please replace the bulb;
  2. When the object stage is rotated, the lower filter would rotate together: because the lower filterfalls off and sticks to the object Please disassemble the object stage, fix the lower filter in the specified position, and then install the stage back,faults can be solved.

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