Test Your Knowledge #8

So you feel you know the Refractometer and how to identify gemstones from using this wonderful piece of Gem Testing Equipment. Let’s see how well you do.

NOTE: Each position indicated in the tables below signifies a gemstone rotation of 45º on the refractometer’s hemi-cylinder. The polarization filter in all cases will be rotated 90º to obtain the lowest and highest RI for each position.

Question#1:

Taking the RI values posted below, what is the:

Optical Character & Sign

Birefringence

What is this stone?

  1st Position 2nd Position 3rd Position 4th Position
Lower RI 1.544 1.544 1.544 1.544
Higher RI 1.551 1.548 1.552 1.553

Questions#2:

Taking the RI values posted below, what is the:

Optical Character & Sign

Birefringence

What is this stone?

  1st Position 2nd Position 3rd Position 4th Position
Lower RI 1.613 1.610 1.614 1.610
Higher RI 1.620 1.619 1.621 1.620

Question#3:

Taking the RI values posted below, what is the:

Optical Character & Sign

Birefringence

What is this stone?

  1st Position 2nd Position 3rd Position 4th Position
Lower RI 1.732 1.732 1.732 1.732
Higher RI 1.732 1.732 1.732 1.732