Ok, so as tends to come up in discussion over the stratum types and their general unbalancedness, we really don't know much about what mineral ratios give what stratums, so, I've decided to start collecting said data:
https://spreadsheets.google.com/ccc?key=0AhPYmdnPan5hdDNncGRIQWFYZ2dmR0R...
I play very frequently, and so will be collecting this data by myself, but this doesn't mean you can't help. Try to get stratums to have ratios differing from these, allowing more diverse data sooner, Guild Collaboration in doing this would be useful.
-Tails-San
Looks like the leading hypothesis is that the top two minerals determine the stratum. The spreadsheet data supports that so far.
Freeze = blue and green
Beast = green and red
Slime = yellow and green
http://wiki.spiralknights.com/Gate_construction#How_Minerals_Affect_Stra...