With just railcraft and no other hightech mod there is no copper/tin worldgen. Is that normal?
Mods | State | ID | Version | Source | Signature | |:------ |:--------------------- |:------------------- |:-------------------------------------------------- |:---------------------------------------- | | LCHIJA | minecraft | 1.12.2 | minecraft.jar | None | | LCHIJA | mcp | 9.42 | minecraft.jar | None | | LCHIJA | FML | 8.0.99.99 | forge-1.12.2-14.23.5.2847.jar | None | | LCHIJA | forge | 14.23.5.2847 | forge-1.12.2-14.23.5.2847.jar | None | | LCHIJA | ivtoolkit | 1.3.3-1.12 | minecraft.jar | None | | LCHIJA | foamfixcore | 7.7.4 | minecraft.jar | None | | LCHIJA | dsurroundcore | 3.5.5.0 | minecraft.jar | None | | LCHIJA | forgeendertech | 1.12.2-4.4.24.0 | ForgeEndertech-1.12.2-4.4.24.0-build.0421.jar | None | | LCHIJA | adhooks | 1.12.2-3.2.2.0 | AdHooks-1.12.2-3.2.2.0-build.0220.jar | None | | LCHIJA | aiimprovements | 0.0.1.3 | AIImprovements-1.12-0.0.1b3.jar | None | | LCHIJA | craftstudioapi | 1.0.0 | CraftStudioAPI-universal-1.0.1.95-mc1.12-alpha.jar | None | | LCHIJA | animania | 1.7.2 | animania-1.12.2-1.7.2.jar | None | | LCHIJA | mantle | 1.12-1.3.3.55 | Mantle-1.12-1.3.3.55.jar | None | | LCHIJA | inspirations | 1.12.2-0.2.8 | Inspirations-1.12.2-0.2.8.jar | None | | LCHIJA | placebo | 1.6.0 | Placebo-1.12.2-1.6.0.jar | None | | LCHIJA | apotheosis | 1.10.4 | Apotheosis-1.12.2-1.10.5.jar | None | | LCHIJA | applecore | 3.2.0 | AppleCore-mc1.12.2-3.2.0.jar | None | | LCHIJA | jei | 4.15.0.268 | jei_1.12.2-4.15.0.268.jar | None | | LCHIJA | appleskin | 1.0.9 | AppleSkin-mc1.12-1.0.9.jar | None | | LCHIJA | thedragonlib | 1.12.2-5.3.0 | thedragonlib-1.12.2-5.3.0.jar | None | | LCHIJA | armorplus | 1.12.2-11.25.1.62 | armorplus-1.12.2-11.25.1.62.jar | None | | LCHIJA | aroma1997core | 2.0.0.2 | Aroma1997Core-1.12.2-2.0.0.2.jar | dfbfe4c473253d8c5652417689848f650b2cbe32 | | LCHIJA | aromabackup | 2.1.1.4 | AromaBackup-1.12.2-2.1.1.4.jar | dfbfe4c473253d8c5652417689848f650b2cbe32 | | LCHIJA | aromabackuprecovery | 2.1.1.4 | AromaBackup-1.12.2-2.1.1.4.jar | dfbfe4c473253d8c5652417689848f650b2cbe32 | | LCHIJA | quark | r1.6-177 | Quark-r1.6-177.jar | None | | LCHIJA | autoreglib | 1.3-32 | AutoRegLib-1.3-32.jar | None | | LCHIJA | ichunutil | 7.2.2 | iChunUtil-1.12.2-7.2.2.jar | 4db5c2bd1b556f252a5b8b54b256d381b2a0a6b8 | | LCHIJA | backtools | 7.0.1 | BackTools-1.12.2-7.0.1.jar | 4db5c2bd1b556f252a5b8b54b256d381b2a0a6b8 | | LCHIJA | baubles | 1.5.2 | Baubles-1.12-1.5.2.jar | None | | LCHIJA | betterbuilderswands | 0.11.1 | BetterBuildersWands-1.12-0.11.1.245+69d0d70.jar | None | | LCHIJA | bettercaves | 1.12.2 | bettercaves-1.12.2-1.5.0.jar | None | | LCHIJA | forgelin | 1.8.4 | Forgelin-1.8.4.jar | None | | LCHIJA | betterfoliage | 2.2.0 | BetterFoliage-MC1.12-2.2.0.jar | None | | LCHIJA | bibliocraft | 2.4.5 | BiblioCraft[v2.4.5][MC1.12.2].jar | None | | LCHIJA | bibliotheca | 1.3.6-1.12.2 | bibliotheca-1.3.6-1.12.2.jar | None | | LCHIJA | blockcraftery | 1.12.2-1.3.1 | blockcraftery-1.12.2-1.3.1.jar | None | | LCHIJA | bloodmoon | 1.5.3 | Bloodmoon-MC1.12.2-1.5.3.jar | d72e0dd57935b3e9476212aea0c0df352dd76291 | | LCHIJA | buildinggadgets | 2.7.3 | BuildingGadgets-2.7.3.jar | None | | LCHIJA | carbonado | 1.5.1 | carbonado-1.5.1-mc1.12.x.jar | None | | LCHIJA | chameleon | 1.12-4.1.3 | Chameleon-1.12-4.1.3.jar | None | | LCHIJA | ctm | MC1.12.2-0.3.3.22 | CTM-MC1.12.2-0.3.3.22.jar | None | | LCHIJA | chisel | MC1.12.2-0.2.1.35 | Chisel-MC1.12.2-0.2.1.35.jar | None | | LCHIJA | chiselsandbits | 14.33 | chiselsandbits-14.33.jar | None | | LCHIJA | clienttweaks | 3.1.11 | ClientTweaks_1.12.2-3.1.11.jar | None | | LCHIJA | clumps | 3.1.2 | Clumps-3.1.2.jar | None | | LCHIJA | codechickenlib | 3.2.3.358 | CodeChickenLib-1.12.2-3.2.3.358-universal.jar | f1850c39b2516232a2108a7bd84d1cb5df93b261 | | LCHIJA | cyclopscore | 1.5.0 | CyclopsCore-1.12.2-1.5.0.jar | bd0353b3e8a2810d60dd584e256e364bc3bedd44 | | LCHIJA | colossalchests | 1.7.3 | ColossalChests-1.12.2-1.7.3.jar | bd0353b3e8a2810d60dd584e256e364bc3bedd44 | | LCHIJA | cookiecore | 2.0.0 | cookiecore-1.12-2.0.0.jar | 4bbb70ebe391f24f7704e343108a9b21b44c1b10 | | LCHIJA | craftingtweaks | 8.1.9 | CraftingTweaks_1.12.2-8.1.9.jar | None | | LCHIJA | crafttweaker | 4.1.19 | CraftTweaker2-1.12-4.1.19.jar | None | | LCHIJA | ctgui | 1.0.0 | CraftTweaker2-1.12-4.1.19.jar | None | | LCHIJA | crafttweakerjei | 2.0.3 | CraftTweaker2-1.12-4.1.19.jar | None | | LCHIJA | customizeddungeonloot | 1.0.3 | Customized-Dungeon-Loot-1.12 -(v.1.0.3).jar | None | | LCHIJA | fastbench | 1.7.2 | FastWorkbench-1.12.2-1.7.2.jar | None | | LCHIJA | cyclicmagic | 1.19.17 | Cyclic-1.12.2-1.19.17.jar | None | | LCHIJA | ding | 1.0.2 | Ding-1.12.2-1.0.2.jar | 4db5c2bd1b556f252a5b8b54b256d381b2a0a6b8 | | LCHIJA | dungeontactics | DT-0.16.6 | DungeonTactics-1.12.2-0.16.6.jar | None | | LCHIJA | csb_ench_table | 1.1.3 | EnchantingTable-1.12-1.1.3.jar | None | | LCHIJA | enchdesc | 1.1.15 | EnchantmentDescriptions-1.12.2-1.1.15.jar | d476d1b22b218a10d845928d1665d45fce301b27 | | LCHIJA | enderstorage | 2.4.6.137 | EnderStorage-1.12.2-2.4.6.137-universal.jar | f1850c39b2516232a2108a7bd84d1cb5df93b261 | | LCHIJA | exchangers | 1.12.2-2.8 | Exchangers-1.12.2-2.8.jar | 4ffa87db52cf086d00ecc4853a929367b1c39b5c | | LCHIJA | shadowmc | 3.8.0 | ShadowMC-1.12-3.8.0.jar | None | | LCHIJA | extrarails | 1.3.0 | ExtraRails-1.12-1.3.0.jar | None | | LCHIJA | familiarfauna | 1.0.11 | FamiliarFauna-1.12.2-1.0.11.jar | None | | LCHIJA | farseek | 2.3.2 | Farseek-1.12-2.3.2.jar | None | | LCHIJA | fastfurnace | 1.3.1 | FastFurnace-1.12.2-1.3.1.jar | None | | LCHIJA | fencejumper | 1.0.5 | fencejumper-1.12-1.0.5.jar | None | | LCHIJA | foamfix | 0.10.7-1.12.2 | foamfix-0.10.7-1.12.2.jar | None | | LCHIJA | friendlyfire | 1.5.10 | FriendlyFire-1.12.2-1.5.10.jar | d476d1b22b218a10d845928d1665d45fce301b27 | | LCHIJA | ftbbackups | 0.0.0.ftbbackups | FTBUtilitiesBackups-1.0.0.12.jar | None | | LCHIJA | futureminecraf | 1.2.1.1 | FutureVersionsV1.2.1.1.jar | None | | LCHIJA | galaxite | 1.1.2 | galaxite-1.1.2-mc1.12.x.jar | None | | LCHIJA | harvest | 1.12-1.2.7-20 | Harvest-1.12-1.2.7-20.jar | None | | LCHIJA | heroicarmory | 1.1.3 | heroicarmory-1.2.0.jar | None | | LCHIJA | hopperducts | 1.5 | hopperducts-mc1.12-1.5.jar | None | | LCHIJA | inventorypets | 2.0.3 | inventorypets-1.12-2.0.3.jar | None | | LCHIJA | ironchest | 1.12.2-7.0.67.844 | ironchest-1.12.2-7.0.72.847.jar | None | | LCHIJA | itemfilters | 1.0.3.12 | ItemFilters-1.0.3.12.jar | None | | LCHIJA | jeiintegration | 1.5.1.36 | jeiintegration_1.12.2-1.5.1.36.jar | None | | LCHIJA | journeymap | 1.12.2-5.5.5 | journeymap-1.12.2-5.5.5.jar | None | | LCHIJA | jeresources | 0.9.2.60 | JustEnoughResources-1.12.2-0.9.2.60.jar | None | | LCHIJA | keywizard | 1.12.2-1.7.1 | keywizard-1.12.2-1.7.1.jar | None | | LCHIJA | kleeslabs | 5.4.12 | KleeSlabs_1.12.2-5.4.12.jar | None | | LCHIJA | laggoggles | FAT-1.12.2-4.8 | LagGoggles-FAT-1.12.2-4.8.jar | None | | LCHIJA | libraryex | 1.0.12 | LibraryEx-1.12.2-1.0.12.jar | None | | LCHIJA | literalascension | 1.12.2-1.0.2.2 | literalascension-1.12.2-2.0.0.0.jar | None | | LCHIJA | longfallboots | 1.2.1a | longfallboots-1.2.1b.jar | None | | LCHIJA | magicfeather | @VERSION@ | magicfeather-1.12.1-2.1.0.jar | None | | LCHIJA | mcjtylib_ng | 3.5.4 | mcjtylib-1.12-3.5.4.jar | None | | LCHIJA | memeinabottle | 2.1.1 | MemeInABottle-1.12.X-2.1.1.jar | None | | LCHIJA | modnametooltip | 1.10.1 | modnametooltip_1.12.2-1.10.1.jar | None | | LCHIJA | moreoverlays | 1.15.1 | moreoverlays-1.15.1-mc1.12.2.jar | None | | LCHIJA | morpheus | 1.12.2-3.5.106 | Morpheus-1.12.2-3.5.106.jar | None | | LCHIJA | mousetweaks | 2.10 | MouseTweaks-2.10-mc1.12.2.jar | None | | LCHIJA | llibrary | 1.7.19 | llibrary-1.7.19-1.12.2.jar | b9f30a813bee3b9dd5652c460310cfcd54f6b7ec | | LCHIJA | mowziesmobs | 1.5.4 | mowziesmobs-1.5.4.jar | None | | LCHIJA | multimob | 1.0.5 | multimob-1.0.5.jar | None | | LCHIJA | naturalbabyanimals | 1.2.0 | naturalbabyanimals-1.2.0-mc1.12.x.jar | None | | LCHIJA | naturescompass | 1.5.1 | NaturesCompass-1.12.2-1.5.1.jar | None | | LCHIJA | neat | 1.4-17 | Neat 1.4-17.jar | None | | LCHIJA | netherex | 2.0.15 | NetherEx-1.12.2-2.0.15.jar | None | | LCHIJA | netherportalfix | 5.3.17 | NetherPortalFix_1.12.1-5.3.17.jar | None | | LCHIJA | recipehandler | 0.13 | NoMoreRecipeConflict-0.13(1.12.2).jar | None | | LCHIJA | norecipebook | 1.2.1 | noRecipeBook_v1.2.2formc1.12.2.jar | None | | LCHIJA | notenoughwands | 1.8.1 | notenoughwands-1.12-1.8.1.jar | None | | LCHIJA | oreexcavation | 1.4.143 | OreExcavation-1.4.143.jar | None | | LCHIJA | oeintegration | 2.3.4 | oeintegration-2.3.4.jar | None | | LCHIJA | openglider | @VERSION@ | OpenGlider-1.12.1-1.1.0.jar | None | | LCHIJA | potioncore | 1.8_for_1.12.2 | PotionCore-1.8_for_1.12.2.jar | None | | LCHIJA | primitivemobs | 1.2.3a | primitivemobs-1.2.3a.jar | None | | LCHIJA | qualitytools | 1.0.7_for_1.12.2 | QualityTools-1.0.7_for_1.12.2.jar | None | | LCHIJA | quarkoddities | 1 | QuarkOddities-1.12.2.jar | None | | LCHIJA | railcraft | 12.0.0 | railcraft-12.0.0.jar | a0c255ac501b2749537d5824bb0f0588bf0320fa | | LCHIJA | randomthings | 4.2.7.3 | RandomThings-MC1.12.2-4.2.7.3.jar | d72e0dd57935b3e9476212aea0c0df352dd76291 | | LCHIJA | reccomplex | 1.4.8.2 | RecurrentComplex-1.4.8.2.jar | None | | LCHIJA | redstonepaste | 1.7.5 | redstonepaste-mc1.12-1.7.5.jar | None | | LCHIJA | reptilemod | 3.8.4 | reptilemod-1.12.2-3.8.4-89.jar | None | | LCHIJA | additionalstructures | 2.3.0 | Rex's-Additional-Structures-1.12.x-(v.2.3.0).jar | None | | LCHIJA | roguelike | 1.8.0 | RoguelikeDungeons-1.12.2-1.8.0.jar | None | | LCHIJA | ropebridge | 2.0.5 | ropebridge-1.12-2.0.7.jar | None | | LCHIJA | ruins | 17.2 | Ruins-1.12.2.jar | None | | LCHIJA | rustic | 1.1.1 | rustic-1.1.1.jar | None | | LCHIJA | signals | 1.4.1-30 | Signals-1.12.2-1.4.1-30-universal.jar | None | | LCHIJA | snad | 1.12.1-1.7.09.16a | Snad-1.12.1-1.7.09.16a.jar | None | | LCHIJA | soundfilters | 0.11_for_1.12 | SoundFilters-0.11_for_1.12.jar | None | | LCHIJA | specialmobs | 1.0.2_for_mc1.12.2 | specialmobs-1.0.2_for_mc1.12.2.jar | None | | LCHIJA | stepup | 1.0.2-mc1.10-1.12.2 | StepUp-1.0.2-mc1.10-1.12.jar | None | | LCHIJA | stg | 1.12.2-1.2.3 | stg-1.12.2-1.2.3.jar | None | | LCHIJA | storagedrawers | 1.12.2-5.4.0 | StorageDrawers-1.12.2-5.4.0.jar | None | | LCHIJA | strawgolem | 1.3 | strawgolem-1.4.1.jar | None | | LCHIJA | streams | 0.4.7 | Streams-1.12-0.4.7.jar | None | | LCHIJA | telepass | 1.0 | TelePass-1.0.jar | None | | LCHIJA | theoneprobe | 1.4.28 | theoneprobe-1.12-1.4.28.jar | None | | LCHIJA | thutcore | 5.21.0 | thutcore-1.12.2-5.21.0.jar | None | | LCHIJA | thutcore_compat | 1.0 | thutcore-1.12.2-5.21.0.jar | None | | LCHIJA | torchmaster | 1.8.0.79 | torchmaster_1.12.2-1.8.0.79.jar | 5e9a436b366831c8f54a7e80b015784da69278c6 | | LCHIJA | ultimate_unicorn_mod | 1.5.16 | ultimate_unicorn_mod-1.12.2-1.5.16.jar | None | | LCHIJA | vanillafix | 1.0.10-SNAPSHOT | VanillaFix-1.0.10-99.jar | None | | LCHIJA | vc | 5.9.13 | ViesCraft-1.12.2-5.9.13.jar | None | | LCHIJA | vulcanite | 1.5.2 | vulcanite-1.5.2-mc1.12.x.jar | None | | LCHIJA | waystones | 4.0.72 | Waystones_1.12.2-4.0.72.jar | None | | LCHIJA | wearablebackpacks | 3.1.4 | WearableBackpacks-1.12.2-3.1.4.jar | None | | LCHIJA | wildcrops | 1.0.1 | WildCrops-1.12-1.0.1.jar | None | | LCHIJA | wolfarmor | 2.2.3.6 | wolfarmor-1.12.2-2.2.3.1798-universal.jar | None | | LCHIJA | xpholder | 2.0.4 | XpHolder-2.0.4-mc1.12.x.jar | None | | LCHIJA | orelib | 3.5.2.3 | OreLib-1.12.2-3.5.2.3.jar | 7a2128d395ad96ceb9d9030fbd41d035b435753a | | LCHIJA | dsurround | 3.5.5.0 | DynamicSurroundings-1.12.2-3.5.5.0.jar | 7a2128d395ad96ceb9d9030fbd41d035b435753a | | LCHIJA | vt | 1.12.2-1.5.5 | VanillaTweaks-1.12.2-1.5.5.jar | None | | LCHIJA | mysticallib | 1.12.2-1.3.8 | mysticallib-1.12.2-1.3.8.jar | None |

Railcraft spawns ore in large mines as seen in this post.

These mines are huge but rare, meaning you have to search for them and can't just dig anywhere.