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Interesting texture. Please share some details. 

This is just calcined Colemanite in some water in a polystyrene cup. See my post in this thread for more context:

http://community.ceramicartsdaily.org/topic/15955-colemanite/

 

I think the lighter coloured bits floating on the water are thin layers of soluble material that have crystallised. You can also see a ring of white crystals above the water line.

Pieter:

When I have chemically etched materials they separate out into carbons, solids, and metals. I would agree soluble salts are clinging to the sides: but by chance are those carbons floating? I do not know what the LOI of colemanite is off the top of my head, or how high you calcined this material.

I stuck the Colemanite in a bisque firing to 915 C, which should be around cone 09. Theoretically, Colemanite has an LOI of 21.9%, but I've seen an analysis of 23.7%. I don't have the exact % weight loss of the sample I used in front of me, but I think it was just over 24%, so I doubt there's much carbon left, if any.