Regarding flux.. I decided to do a little testing, used a worldgen I made in the past day or so, and generated 10 worlds with it.
Testing parameters (using vanilla 34.07):
Worldgen
[WORLD_GEN]
[TITLE:FLUX_TEST1]
[DIM:65:65]
[EMBARK_POINTS:2500]
[END_YEAR:250]
[BEAST_END_YEAR:250:99]
[REVEAL_ALL_HISTORY:0]
[CULL_HISTORICAL_FIGURES:1]
[ELEVATION:100:400:101:101]
[RAINFALL:10:32:101:101]
[TEMPERATURE:90:90:0:0]
[DRAINAGE:10:49:101:101]
[VOLCANISM:0:0:0:0]
[SAVAGERY:0:0:0:0]
[ELEVATION_FREQUENCY:3:8:0:0:0:2]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[MINERAL_SCARCITY:500]
[MEGABEAST_CAP:0]
[SEMIMEGABEAST_CAP:0]
[TITAN_NUMBER:0]
[TITAN_ATTACK_TRIGGER:80:0:0]
[DEMON_NUMBER:0]
[NIGHT_TROLL_NUMBER:0]
[BOGEYMAN_NUMBER:0]
[VAMPIRE_NUMBER:0]
[WEREBEAST_NUMBER:0]
[SECRET_NUMBER:0]
[REGIONAL_INTERACTION_NUMBER:0]
[DISTURBANCE_INTERACTION_NUMBER:0]
[EVIL_CLOUD_NUMBER:0]
[EVIL_RAIN_NUMBER:0]
[GOOD_SQ_COUNTS:0:0:0]
[EVIL_SQ_COUNTS:0:0:0]
[PEAK_NUMBER_MIN:0]
[PARTIAL_OCEAN_EDGE_MIN:0]
[COMPLETE_OCEAN_EDGE_MIN:0]
[VOLCANO_MIN:0]
[REGION_COUNTS:SWAMP:0:0:0]
[REGION_COUNTS:DESERT:0:0:0]
[REGION_COUNTS:FOREST:0:0:0]
[REGION_COUNTS:MOUNTAINS:0:0:0]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:1000]
[RIVER_MINS:800:800]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:0]
[SUBREGION_MAX:2750]
[CAVERN_LAYER_COUNT:1]
[CAVERN_LAYER_OPENNESS_MIN:10]
[CAVERN_LAYER_OPENNESS_MAX:15]
[CAVERN_LAYER_PASSAGE_DENSITY_MIN:0]
[CAVERN_LAYER_PASSAGE_DENSITY_MAX:0]
[CAVERN_LAYER_WATER_MIN:10]
[CAVERN_LAYER_WATER_MAX:15]
[HAVE_BOTTOM_LAYER_1:1]
[HAVE_BOTTOM_LAYER_2:1]
[LEVELS_ABOVE_GROUND:1]
[LEVELS_ABOVE_LAYER_1:40]
[LEVELS_ABOVE_LAYER_2:16]
[LEVELS_ABOVE_LAYER_3:2]
[LEVELS_ABOVE_LAYER_4:2]
[LEVELS_ABOVE_LAYER_5:3]
[LEVELS_AT_BOTTOM:2]
[CAVE_MIN_SIZE:1]
[CAVE_MAX_SIZE:1]
[MOUNTAIN_CAVE_MIN:0]
[NON_MOUNTAIN_CAVE_MIN:0]
[ALL_CAVES_VISIBLE:1]
[SHOW_EMBARK_TUNNEL:2]
[TOTAL_CIV_NUMBER:2]
[TOTAL_CIV_POPULATION:5000]
[SITE_CAP:10]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:0:0:0]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]
note Mineral Scarcity: 500. One cavern. No volcanism, no volcanos. Mountains and plains only. Plains were all elevation 100. All embarks were found on the plains.
Finder ParametersEmbark Dimensions - 4x4
Flux Stone - Yes
Aquifer - No
Shallow Metal - Multiple
Deep Metal - Multiple
Flux is: Calcite, Chalk, Dolomite, Limestone, Marble
10 random worlds with above worldgen, vanilla 34.07, results are..
Marble Y/N First Stone under soil level(s)
---------- -------------------------------
Y Dolomite
Y Limestone
Y Shale
Y Siltstone
Y Phyllite
Y Claystone
Y Chert
Y Shale
Y Siltstone
Y Siltstone
Y Marble Every single map met the finder criteria, and every single time, finder was correct. Verified with dfhack 'prospect hell' and 'reveal'.
Every embark had Marble, at minimum.However, it sometimes did this by combining two biomes to get all the parameters to match.
Biome1 could have Shallow metals
Biome2 could have Deep Metals, and Flux
So when you view it, initially, you think, no flux! But if you press F2, you see flux, and if you embark, flux is there.
Even if it's just Marble, 100% (10/10) of all worlds made with that worldgen, there was flux, and the finder worked exactly as expected.
I'll be happy to do another round of tests if someone has some constructive criticism/suggestions to debunk some of the myths.