dichroism

He also studied the orientation of purines and pyrimidines in tobacco mosaic virus and in nucleic acids, by measuring the ultraviolet dichroism of oriented specimens, and he studied, with the visible-light polarizing microscope, the arrangement of virus particles in crystals of TMV and measured dry mass in cells with interference microscopes.

Maurice Wilkins - Biography 1964

If now a stone that exhibits dichroism is held in front of the square hole and viewed toward the light, two images of the stone are seen, one due to its ordinary ray (which, as was said above, will have one color), and the other due to its extraordinary ray (which will have a different color or shade of color), thus the color of the two squares will be different.

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

Not all stones that are doubly refracting exhibit dichroism.

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

Also, owing to the dichroism of the ruby the red is variable according to the changing position of the stone.

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

Purple spodumene (kunzite) is pinkish to lilac in shade -- usually pale, unless in large masses, and it shows very marked dichroism.

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

Although strongly doubly refracting, the hyacinth shows scarcely any dichroism and thus lacks variety of color.

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

And as in some real rubies there are found slight hollows corresponding or analogous to the bubbles found in melted glass, it becomes a matter of great difficulty to distinguish the real from the imitation by such tests as hardness, specific gravity, dichroism, and the like, so that in such a case, short of risking the ruin of the stone, ordinary persons are unable to apply any convincing tests.

The Chemistry, Properties and Tests of Precious Stones John Mastin

Almandine garnets also show no dichroism and lack variety of color.

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

This stone is doubly refracting, exhibiting extremely strong dichroism, especially in the blue and the green varieties.

The Chemistry, Properties and Tests of Precious Stones John Mastin

The stronger dichroism of the tourmaline frequently reveals itself to the naked eye, and there is usually one direction or position in which the color of the stone is very inferior to its color in the opposite direction or position.

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