Hi,
I let some seawater dry slowly on a slide over 24 hours and had a look under crossed polars. There were some lovely large NaCl crystals, which aren't anisotropic, but there were also some much smaller crystals which were. They weren't coloured under cross polarisation but they looked nice with a lambda plate inserted.
I assume that they are some sort of salt, possibly a sulphate, if any one knows what they are likely to be I'd appreciate the info.
Here's a collage of a few of the crystals, crossed polars with a lambda plate, Epi illumination, 20x objective.
Dave
Sea Water Salts
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Sea Water Salts
Last edited by micro_pix on Tue Jul 28, 2020 12:47 am, edited 1 time in total.
-
- Posts: 1527
- Joined: Mon Jan 15, 2018 9:23 pm
- Contact:
Re: Sea Water Salts
Wow they look like small fluorite crystals, love the colour!
Re: Sea Water Salts
.
Thanks for the input Marco and Pau.
I googled the concentration of the ions in seawater and after Chloride (0.546 moles/kg) Sulphate (0.0282 moles/kg) is the next most abundant anion, Ca is third most abundant cation. I also found a paper that covers the deposition of salts during seawater evaporation and all of the information points to Pau’s suggestion of CaSO4. Another interesting paper on crystal growth that looks at Halite, Calcite and Gypsum crystals.
Dave
Thanks for the input Marco and Pau.
I googled the concentration of the ions in seawater and after Chloride (0.546 moles/kg) Sulphate (0.0282 moles/kg) is the next most abundant anion, Ca is third most abundant cation. I also found a paper that covers the deposition of salts during seawater evaporation and all of the information points to Pau’s suggestion of CaSO4. Another interesting paper on crystal growth that looks at Halite, Calcite and Gypsum crystals.
Dave