There's a purify reaction for every soil type, except for pure clay and sands. This means, purify sandy loam, sandy clay, loam, clay loam, ect... I also made them all gatherable.
Every reactions has a chance of giving sand, mud and clay. The chances vary with every soil type. Here is for example the reaction with Loam:
[REACTION:KOBOLD_PURIFY_LOAM]
[NAME:Purify loam]
[BUILDING:DIRT_DIGGER:NONE]
[REAGENT:BAG:1:BOX:NONE:NONE:NONE][EMPTY][BAG][PRESERVE_REAGENT][CAN_USE_ARTIFACT]
[REAGENT:BUCKET:1:BUCKET:NONE:NONE:NONE][EMPTY][PRESERVE_REAGENT][CAN_USE_ARTIFACT]
[REAGENT:CLAY:1:BOULDER:NONE:INORGANIC:LOAM]
[PRODUCT:40:1:POWDER_MISC:NONE:INORGANIC:SAND_TAN][PRODUCT_DIMENSION:150][PRODUCT_TO_CONTAINER:BAG]
[PRODUCT:20:1:BOULDER:NONE:INORGANIC:CLAY]
[PRODUCT:40:1:LIQUID_MISC:NONE:INORGANIC:SILT][PRODUCT_DIMENSION:150][PRODUCT_TO_CONTAINER:BUCKET]
[SKILL:MILLING]
Anyway, I replaced mud with silt (liquid) and added this to the silt entry:
YESSSC[INORGANIC:SILT]
[USE_MATERIAL_TEMPLATE:SOIL_TEMPLATE]
[DISPLAY_COLOR:7:0:1][TILE:142]
[STATE_NAME_ADJ:ALL_SOLID:silt]
[STATE_NAME_ADJ:LIQUID:muddy silt]
[SOIL][AQUIFER]
[SPEC_HEAT:4181]
[MELTING_POINT:10000][BOILING_POINT:10180]
[LIQUID_DENSITY:1800][SOLID_DENSITY:1600]
[MATERIAL_REACTION_PRODUCT:FIRED_MAT:INORGANIC:GREENWARE_CLAY]<--Just be gathered
I still have to test this one, but, do you see anything wrong?
EDIT: Silt seems to work now.