dichroscope

To aid in the examination of this wonderfully beautiful property possessed by precious stones, a little instrument has been invented called the dichroscope, its name showing its Greek derivation, and meaning -- "to see colour twice" (twice, colour, to see).

The Chemistry, Properties and Tests of Precious Stones John Mastin

The only imitation (scientific rubies and sapphires are not here classed as imitations), which is at all likely to deceive one who knows how to use the dichroscope is the emerald triplet, made with real (but pale) beryl above and below, with a thin strip of green glass between.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

The dichroscope also serves to detect the false character of doublets and paste imitations, as neither shows dichroism.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

To one skilled in these matters only a few seconds are required for the inspection of a stone with the lens, the dichroscope, or the refractometer, and hardness tests are swiftly made.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

The use of a dichroscope would have saved them that error, for the stone is singly refracting.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

The dichroscope (which might have been used much earlier in the test but was not at hand at the time) was next tried and the stone was seen to have marked dichroism -- a bluish green and a yellowish green appearing in the two squares of the instrument when the stone was held in front of the opening and viewed against a strong light.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

The difference was so marked as to be easily seen without the dichroscope.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

To find out with a finished stone whether or not the lapidary has cut it properly as regards its optical properties one may use the dichroscope, and if there is little or no dichroism in evidence when looking through the table of the stone it is properly cut.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

Where a sapphire shows a poor color and the dichroscope shows that the table was laid improperly, there is some possibility of improving the color by recutting to the above indicated position.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade

The student should, if possible, obtain the use of a dichroscope and practice with it on all sorts of stones.

A Text-Book of Precious Stones for Jewelers and the Gem-Loving Public Frank Bertram Wade