The custom ore bitmap is relatively simple, but perhaps more complex than you’d expect. It’s just a side effect of how the system works. You fill in a 1 for an ore you want, and a 0 for any ore you don’t.
The order of ores is:
Arkonor
Bistot
Crokite
Gneiss
Hedbergite
Hemorphite
Jaspet
Kernite
Mercoxit
Omber
Spodumain
Plagioclase
Pyroxeres
Scordite
Veldspar
Dark Ochre
So, to allow all but Crokite, you’d use: 1101111111111111