@dulciknit Thanks, Alison - I have to confess, i just had to google 'geode slice' as I've not heard that term before, but yes, I see what you mean! :o)
@phil_howcroft Thanks - I wondered about doing the crop - especially as I had a finger/thumb in the pic from where I was holding the slice up to the light! But I kinda like how the light catches on the little hairs around the edge, so I did a hasty crop/rotattion/collage job instead. So, I wonder, had you noticed the mirror image and not-very-good join? lol