FMF - Friends of Minerals Forum, discussion and message board

[Gerhard Niklasch]

Recently I've added a polarizing filter to my microphoto toolbox.

So for comparison, below is a composite of six views, two along each axis, of the Zoisite var.Tanzanite from earlier in this thread (https://www.mineral-forum.com/message-board/viewtopic.php?p=12431#12431).

Shown from top to bottom: the sides which would be pale blue, pale violet, and purple without the filter. The filter is in the horizontal position in the three images on the left, in the vertical position on the right, as indicated by the black lines.

So the "pale blue" is really a composite of green and blue-violet components, polarized in different planes! I didn't know this before.

I haven't yet got round to re-doing a photo of the little Uvite that had also featured in the above posting, but the effect on it is easy to describe in words: Seen from the side with the filter (thus E vector) parallel to the c axis, it stays bright pale green; with the filter at right angles to c, it turns the same darker mauve-ish shade as when viewed down the c axis (where E is automatically orthogonal to c).

Enjoy,
Gerhard

[Matt_Zukowski]

Thanks Gerhard...interesting