Found out about this website from today's Geology Hub uploaded on YT
https://www.youtube.com/watch?v=v75f530yFOY
This crystal doubles images, meaning that if you look through it that anything on the other side whether that be text, a person, or a photo of a volcano will appear to be doubled. But, why does this unusual optical property occur when utilizing a crystal of calcite? The answer is a fascinating phenomenon known as birefringence, which this video will explain through the expertise and analysis of a geologist.
This is the about-page of which text continues past the posted image on the left side:
https://www.mindat.org/a/aboutmindat
Here is the link to the discussion groups page pictured:
https://www.mindat.org/discuss.php
And as a further aside, the image was made with an F-Droid app that is new to me but popped up 3 months ago apparently and has a lot of great features for stitching images and creating content:
That's awesome!
That's rigjt up there with the ROCKD app.