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Prospecting for limestone/chalk Guide

Silent Shadow

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I haven't really found any advice for sourcing limestone or chalk besides go look for it and basalt can spawn over it. Seeing how the lack of limestone/chalk will hold you back pretty hard, and the only alternative to mining is purchasing the small supply from the traders, I thought I would share my method, which makes use of the propick. Though it is still possible to search without one early on, I would recommend rushing to a copper propick just after a hammer and pickaxe since they can be made without an anvil (with molds), and then searching with one as it saves a lot of time and lives exploring dangerous shafts and tunnels.

From cruising around in creative I have found the following:

  • If you find any sedimentary rocks on the surface then the chance of another sedimentary rock layer lying below seems quite small, and the chance of sublayers being chalk or limestone seems to be just as unlikely.
  • Sedimentary rocks seem to always be the top layers, with the sole exception of basalt, which is usually on top but may be sandwiched between sedimentary rock layers (seen with shale on top, not sure if that's related though).
  • Rock type is consistent over horizontal distances ranging from 500 blocks to over 2000 blocks. Hope you like exploring.
  • Rock type is consistent over vertical distances ranging from a few blocks to over 50 blocks. Hope for mountains or deep shafts.
  • Spotting rock types in the map can be difficult due to the subtle shading differences of sand, gravel, and stone to the point that limestone/chalk may appear as granite or conglomerate.

From comparing ores, minerals, and gems to their parent "gangue" rocks we can find some use in using a propick density mode search:

  • Malachite is only found in limestone and the much rarer three marbles (from what I've seen they don't spawn and I have never seen them). So finding malachite probably means you've found limestone.
  • Kernite, Galena, sulfur, phosphorite, borax, and the three coals (not graphite) are only found in 7 of the 8 sedimentary rocks (not bauxite), so finding one of those means there is a ~29% chance there is limestone or chalk (assuming there is an equal chance for all sedimentary rocks to form).
  • Hematite may indicate limestone (but not chalk) but also may indicate sandstone, peridotite, phyllite, or granite
  • Finding Limonite may mean the sedimentary layer is Chert or Shale and not limestone nor chalk, but this may just be Basalt rock. (If ore grade is better with higher density searches than very high and ultrahigh densities may rule out that the ore is in basalt. I don't really know though, nor have I found anything to suggest this aside from common sense)
  • Lapis Lazuli only spawns in limestone, bauxite, and in the rare three marbles, making it a good indicator of a maybe 50% chance (I have yet to see any marble in the game but it may just be super rare).
  • I found that Halite seems to spawn near limestone more than any other sedimentary rock, but I could not find any positive source to back this up. Something to consider though. I would appreciate hearing others' experiences on this.

Taking all that info into account, it would seem that the best method for finding limestone or chalk would be:

  • Keep an eye out for it while not in the map, as you may get lucky. Using the map for this is not recommended as limestone and granite have very similar colors and gravel, sand, and stone all have slightly different shades, but when passing over you may as well check.
  • Keep an eye out for bits in the world for Malachite, Lapis Lazuli, Kernite, Halite, Galena, sulfur, phosphorite, borax, and the three coals (not graphite). While most of these are rare, they may indicate a sedimentary layer below a layer of dirt, and possibly be limestone. Chances are though that if it is limestone, you will have seen it in rock, gravel, or sand form before chancing upon the bits.
  • Search the surface world for Basalt and do a propick density test survey of the region. Note any mountains and deep looking shafts on the map as they can be used to confirm findings.
    • If malachite is found, you've almost certainly found limestone (or the useless marble, which I am unsure exists at all as I have yet to see it naturally)
    • If Halite (salt) is found, you've probably found limestone.
      • Disclaimer: I have not found any source to back up my correlation of halite to limestone other than the requirement to spawn in a sedimentary rock layer (but I rarely find them in other stones which may be from a lack of testing), so confirm with a mountain or deep shaft.
    • If Lapis Lazuli is found, you've found limestone or bauxite (or again, useless marble). A tighter propick survey pattern is more likely to detect Lapis Lazuli.
      • Confirm with a mountain or a deep shaft. Confirm with tunnel exploration if you must, or just dig/mine a shaft down. Expect to go 50-100 blocks or more to find limestone.
    • If Kernite, Galena, Phosphorite, Borax, Halite, Sulfur, or a coal (lignite/brown, bituminous/black, or anthracite), then there is a decent chance of chalk or limestone being there if limonite is not detected.
      • Consider doing more propick surveys to detect an above marker, or look for a mountain. If these turn up nothing, then consider an exploration of a shaft, but don't get your hopes up.
    • If Lapis Lazuli and one of [Kernite, Galena, Halite, Phosphorite, Borax, Sulfur, or a coal (lignite/brown, bituminous/black, or anthracite)] are found then you probably have found limestone as bauxite does not spawn with the latter.
      • Confirm with a mountain or deep shaft. There is a chance you have found a double sedimentary rock layer under basalt, but that is rare (in my experience anyway).
    • If hematite is detected, then there is a chance limestone lays below, but it is unlikely as hematite can be found in 5 types of rock (see above).
      • Further propick surveys are recommended, but if an above marker is not found, I wouldn't get my hopes up. Move on, unless also searching for iron ores, as you may get a rare mine that yields iron and limestone.
    • If Limonite is found and none of the top three markers, there probably is no Chalk nor Limestone layer, so move on.
  •  Also look for surface sedimentary rock layers (Bauxite, Sandstone, Claystone, Conglomerate, Chert, Shale) though they are much less likely to contain limestone, you will probably be passing over them and so may as well do a quick check with a propick. If you're searching before having a propick I would recommend skipping them unless they have high mountain cliffs.
    • If you see a mountain cliff, and see a non-sedimentary rock layer below the sedimentary rock layer, move on; there's no limestone nor chalk.
      • If you see basalt, there is a rather small chance of limestone, so use the propick or move on.
    • Do a propick survey.
      • If you found malachite, you found limestone. Probably.
      • If Lapis Lazuli is found and not in a surface bauxite layer, you may have found limestone.
        • If Kernite, Galena, Halite, Phosphorite, Borax, Sulfur, or a coal (lignite/brown, bituminous/black, or anthracite) is also found, then chalk or limestone is likely, but may be deep.
          • Confirm with a mountain or a deep shaft, there is still a chance that you got a different sedimentary rock than chalk or limestone.
        • Confirm with mountain or deep shaft. You may get unlucky with bauxite below. In rare cases, you may get limestone and bauxite spawn below the top sedimentary layer but multiple sedimentary layers are unusual and three or more are rare (in my experience anyway).
      • If limonite is found and not in a surface layer of chert or shale, there is probably no limestone or chalk and you should move on.
  • Finding any other type of rock (Andesite, Granite, Peridotite, Phyllite, Slate (not shale), or kimberlite (if that's possible on the surface)) on the surface probably means there is no limestone nor chalk below and you should move on.
    • However, if a propick shows Malachite, Lapis Lazuli, Kernite, Halite, Galena, Phosphorite, Borax, Sulfur, or a coal (lignite/brown, bituminous/black, or anthracite) then there must be a sedimentary rock layer below, possibly limestone or chalk, BUT this is very irregular (in my experience anyway) and you should not expect this to happen with non-basalt, non sedimentary surface rock layers, so don't waste your time checking them out but be mindful while searching for other ores like tin or copper.


Hopefully this will save you some time, but you should still be prepared to spend an hour or more.

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Also marble apparently only spawns in phyllite and slate (see third link) so if you also see graphite with malachite then it may not be limestone but a metamorphic rock. It could be both too, so check with a mountain or deep shaft.

Also, just because you find limestone sand or gravel on the surface does not mean there will be limestone rock below. Confirm it by digging down to rock.

Edited by Silent Shadow
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  • 2 weeks later...
  • 2 years later...
4 hours ago, Aryan van der L said:

With the prospecting pick just giving chunk chance indication it kind of feels useless, since the chunk is 32X32 finding something is more a roll of the dice then anything else eating through your pickaxe and food reserves.

Managed to break 6 or so not finding anything useful.

Here's something mind blowing. It's not actually chunk based. You are likely looking at the chunk map from the Prospecting Mod thinking that it is. It's purely location based.

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