Brains
Well-known member
I am sure many of us have noticed in underground places, particularly old mines, tunnels and man made structures, but also in natural places, very fine needle like crystals growing in mats on the walls. I had always thought of these as gypsum or selenite, possibly aragonite. I have also noticed these growths are somewhat seasonal, either growing or completely vanishing. I had heard they could be a nitrate based evaporite, rather than sulphate or carbonate, probably a hydrate. The needles seem to age in to a more nodular popcorn type surface with fewer obvious needle like features. Rarely the crystals can be up to 15mm, but more usually 5mm is a more common length
Does anyone out their have any more info, ideas, thoughts?
This poor photo from Cwmorthin shows such a mat of fine crystal needles
Does anyone out their have any more info, ideas, thoughts?
This poor photo from Cwmorthin shows such a mat of fine crystal needles