Where Allthemodium ore generates
The short answer
Allthemodium ore generates in three places in All the Mods 10 8.2, and the pack adds no fourth. That was checked in 8.2, 0.34, 0.57, 0.59 and 4.5. All three are low. None of them is a mountain.
The Deep Dark biome, not the ancient city. Ten attempts a chunk, vein size 4, from the world floor up to Y 10, on a cave ceiling and exposed to air. Go to The Deep Dark.
The Mining Dimension, between Y 65 and Y 129, one attempt a chunk, vein size 4. That is the deepslate band. The book's Y -59 to 20 is wrong. Go to The Mining Dimension.
The Other, the same ten attempts as the Deep Dark, and only where the block is deepslate: from that dimension's floor up to about Y 8. Go to The Other.
The Deep Dark is denser than the Mining Dimension, ten attempts against one. The Other uses the same ten, so this page does not rank those two against each other. How many of the attempts you actually see depends on cave ceiling and on how much of The Other is deepslate, and no file states that.
The in-game book is wrong about the mountains and about the Mining Dimension's height. Read What the book gets wrong before you follow it. The pack's own tooltip agrees with the files and leaves The Other out: What the item tooltip says.
A machine that deletes the ore is a different problem, and this page does not cover it.
Checked against: Allthemodium 3.0.1.
On this page
Applies to Allthemodium 3.0.1, Minecraft 1.21.1, NeoForge 21.1.251, as shipped in All the Mods 10 8.2. The book's ore page is the same text in Allthemodium 2.6.03, 2.6.9, 2.7.0, 2.9.3 and 3.0.1, and the two placed features behind the numbers below are byte-identical across those five jars. Allthemodium 2.3.1 and 2.5.5 already carry the same three ore modifiers and the same book text. Jars older than 2.3.1 were not read.
The Deep Dark
In Allthemodium 3.0.1, as shipped in All the Mods 10 8.2, one biome modifier adds the ore to the biome minecraft:deep_dark and to nowhere else in the overworld. The feature is allthemodium:allthemodium_ore. It is the deep dark biome, not the ancient-city structure. A player who only searched the city was in one place inside that biome.
The feature makes ten attempts a chunk, vein size 4. The height runs from the dimension's own floor up to Y 10. This page does not print that floor as a number: the feature says the dimension's bottom, and the overworld's bottom is not in a file this page cites. Each attempt looks up through air, at most 12 blocks, for a sturdy face, then places one ore below it, so the ore sits on a cave ceiling and is exposed to air. In deepslate the block placed is allthemodium:allthemodium_slate_ore. In stone it is allthemodium:allthemodium_ore.
Ten attempts here against one in the Mining Dimension is the comparison the files support. The Other uses this same feature, so the Deep Dark is not the densest of the three.
The same placed feature, the same count, and the same height are in Allthemodium 2.6.03, 2.6.9, 2.7.0, 2.9.3 and 3.0.1. What was checked in 2.3.1 and 2.5.5 is that this modifier is present, not that those two jars' height numbers were read line by line.
Sources: Allthemodium 3.0.1 data/allthemodium/worldgen/placed_feature/allthemodium_ore.json, data/allthemodium/worldgen/configured_feature/allthemodium_ore.json, and data/allthemodium/neoforge/biome_modifier/allthemodium/allthemodium.json.
The Mining Dimension
In Allthemodium 3.0.1, as shipped in All the Mods 10 8.2, the Mining Dimension uses a separate feature, allthemodium:allthemodium_mining, added to the mining biomes. It places the ore once per chunk, vein size 4, between Y 65 and Y 129. That is the deepslate band.
The book's band, everywhere between Y -59 and Y 20, is not this feature. Y 65 to 129 is where it places, and it does not place in the layers below that.
The Deep Dark's feature attempts ten times a chunk. This one attempts once, vein size 4, across that Y band.
The placed feature is byte-identical in Allthemodium 2.6.03, 2.6.9, 2.7.0, 2.9.3 and 3.0.1, including the height of 65 to 129. In 2.3.1 and 2.5.5 the modifier that adds this feature is present; those two jars' height lines were not compared.
Sources: Allthemodium 3.0.1 data/allthemodium/worldgen/placed_feature/allthemodium_mining.json and data/allthemodium/neoforge/biome_modifier/allthemodium/dim_ores/ore_allthemodium.json. The configured feature is the same allthemodium_ore file as the Deep Dark, vein size 4.
The Other
In Allthemodium 3.0.1, as shipped in All the Mods 10 8.2, The Other gets the same feature as the Deep Dark: allthemodium:allthemodium_ore, ten attempts a chunk, vein size 4, from the dimension's floor up to Y 10. The modifier targets #allthemodium:mining_features/other_features, which is The Other's own biomes: soul sand valley, desert hills, desert, warped forest, crimson forest, and the_other. It is not a second, richer placement.
The dimension's bulk block is ancient stone, and ancient stone is not in the stone-ore replaceables tag inside this mod. Deepslate is the block at and below Y 0, mixed with ancient stone up to Y 8, and ancient stone above that. The ore can replace that deepslate, so the working band is the world floor up to about Y 8. The feature stops at Y 10 anyway. The Other's own dimension type sets that floor at Y -64. That number is this dimension's. It is not a number for the overworld.
How much of The Other is deepslate is not in a file, so the ten attempts are not a count of the ore you will see. The same ten-attempt feature is byte-identical in Allthemodium 2.6.03, 2.6.9, 2.7.0, 2.9.3 and 3.0.1. In 2.3.1 and 2.5.5 the modifier is present; the deepslate gradient was not re-read there.
Sources: Allthemodium 3.0.1 data/allthemodium/neoforge/biome_modifier/allthemodium/the_other/allthemodium.json, the same placed_feature/allthemodium_ore.json as the Deep Dark, data/allthemodium/worldgen/noise_settings/the_other.json for the ancient-stone bulk and the deepslate gradient, and data/allthemodium/dimension_type/the_other.json for the floor at Y -64.
What the book gets wrong
No mountain, peaks, windswept, grove, meadow, slope or hill biome is in the mod's biome modifiers. The mountain sentence has no file behind it. It has not been true in anything All the Mods 10 has shipped. Jars older than 2.3.1 were not read, so this page does not say the line was never true before then.
The ore is added in exactly three places, and All the Mods 10 adds none of its own. That pack-level check was made in 8.2, 0.34, 0.57, 0.59 and 4.5: no pack datapack, no KubeJS data file and no KubeJS runtime generator places the ore, and nothing in those editions removes the three the mod adds.
Sources: the book entry assets/allthemodium/patchouli_books/allthemodium_book/en_us/entries/ore/allthemodium.json in the jars named above. The pack-level negative is the 23 September 2026 correction in the same research file, read against those five pack editions.
What the item tooltip says
All the Mods 10 8.2's tooltip on allthemodium:allthemodium_ore and allthemodium:allthemodium_slate_ore says "Found in the Deep Dark Biome and will always spawn air exposed" and "Also found in the Deep Slate Layer of Mining Dimension." No mountains. It does not mention The Other, so the tooltip is right about what it names and incomplete about the third place.
That text is byte-identical in All the Mods 10 0.57, 0.59 and 4.5. All the Mods 10 0.34 ships no kubejs/client_scripts directory, so it has no tooltip to agree or disagree. On 0.34 the mountain claim rests on the jar alone, which still has no such placement.
Sources: overrides/kubejs/client_scripts/tooltips.js in the All the Mods 10 8.2, 0.57, 0.59 and 4.5 pack zips, and the absence of kubejs/client_scripts in the 0.34 zip.