Talk:Pleochroism

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Question: if double refraction splits into 2 beams at 90° angles polarized, and this leads to the dichroic effect; are trichroic stones split into 3 beams at what angles?

I wonder if you misunderstood. I think the author meant the two orthagonal (ie perpendicular, 90°) polarization states see different refractive indicies and thereby split into two paths. For a given wavelength, you should only be able to split it in two.

Question: Is this description of Pleochroism accurate? As far as i know, pleochroism is not only caused by a coloured gem or crystal,but by any mineral that has pleochroic properties such as biotite. does the name gem or crystal cover all minerals? Also, from how i read this article it seems that as the stage is rotated, the colours observed change for a mineral. this is the birefringence or the orientation at which the mineral is observed at under cross polarised light. Is pleochroism not the property of varying colour intensity within a mineral when the stage is rotated in plane polarised light? The author also makes it seem as though pleochroism is visible by the naked eye, is this not a phenomena that is only visible under a petrographic microscope? 203.160.127.213 04:04, 17 June 2007 (UTC)

This article definately needs improvement. The next contributer needs to have a deeper understanding. In part answer, you do not need a microscope, but it helps to see tiny crystals. This property could apply to any transparent substance, including minerals, it does not have to be a gem or crystal. I am hoping to see some good examples listed here, or more detail on how it is measured or described. GB 07:39, 27 June 2007 (UTC)

Examples of pleochroic minerals would be Really Good. Preferably with pictures. —Quasirandom 14:25, 15 August 2007 (UTC)

You can easily see pleochroism in some hand samples. It does not necessarily occur as varying intensity, but can actually be different colors. Birefringence, I believe, is similar but is observed only in thin section. If someone doesn't beat me to it, I might try to expand this article with examples. Professor Chaos (talk) 04:47, 12 December 2007 (UTC)

Some excelent examples to include, if you can find good slide images, would be a prismatic section of Tourmaline, with a strong pleochroic scheme of blue to pink, as well as biotite. These would clearly demonstrate that both variations in color intensity, as well as hue, are possible. A question for pleochroism in hand sample: If a mineral is pleochroic in thin section under PPL, will it neccesarily exhibit the same pleochroism under hand sample and non-polarized light? Boz3030 (talk) 07:55, 23 December 2007 (UTC) P.S: As to how it is measured or described: It is somewhat subjective in that it would be described as weak, moderate or strong pleochroism, generally with the pleochroic scheme given. My previous examples are strongly pleochroic, where a mineral like Epidote is an example of one showing weak pleochroism.