A coal miner's guide - Spark and furnace values included

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Hi everyone, while playing the game I’m finding plenty of higher metals I want to smelt and process, but it turns out more fuel is always needed for smelting metals and converting into spark for processing.

I wasn’t entirely satisfied with the existing thread about spark values for fuels and I wanted to answer for myself two questions:

  1. Are some fuels more efficient to use in the furnace than in Spark cores?
  2. Which coal type should I hunt for when I urgently need spark?

It was time for science, of which you can see the results below:


                   Spark Value  Time (s)  Spark/s  Spark per coal  Bonus for compacting  Furnace Cycles  Cycles/coal  Bonus for compacting  Spark / Cycle
Peaty Soil           20           7,5      2,6667                                         0,125                                              160
Wood Trunk/Timber    30           7,5      4                                              0,2                                                150
Soft Coal           100          10       10                                              0,55                                               181,8182
Medium Coal         250          15       16,6667                                         1,3333                                             187,5
Hard Coal           800          30       26,6667                                         4                                                  200
Compact Peat        300          60        5         41,6667      108.33%                 2              0,2777      122,22%                 150
Compact Soft Coal  1200         120       10        166,6667       66,67%                 6,6666666667   0,9259       68,35%                 180
Compact Coal       3000         180       16,6667   416,6667       66,67%                16,6666666667   2,3148       73,61%                 180
Compact Hard Coal  9600         360       26,6667  1333,3333       66,67%                52,6666666667   7,3148       82,87%                 182,2785

From this table, question 1 is answered: Compact Peat is the most efficient fuel to use for smelting, followed by the potentially more practical Compact Soft Coal or Compact Coal. Compact Hard coal is very slightly less efficient, better spent in a spark core. Peaty Soil and Wood are also surprisingly efficient, best used in a furnace if you have excess. (mass convert to compact peat and timber first) But given the huge amounts needed to smelt things you shouldn’t harvest peaty soil or wood over coal.

For question 2 I still don’t have a clear answer since this strongly depends on the abundance of coal veins, average vein yield and time taken to find them.

But I can give some recommendations:

Hard Coal

Never skip a Hard Coal vein if you come across one when caving. Each block mined is worth 8 soft coal pieces.

Can be found reliably near lava level anywhere on the planet. Probably not a very good time investment if you don’t also need gold/silver/titanium because of the small vein sizes and difficulty navigating around lava lakes.

Medium Coal

Worth picking up while searching for other ores if you’re not in a hurry or low on fuel. Each block is worth 2.5 soft coal pieces.

Medium coal strikes a good balance in harvesting efficiency and block value. It’s not worth as much as hard coal but the larger vein sizes make up for it and it is less dangerous to gather. They’re concentrated in certain resource rich areas of a planet (which also tend to have iron and copper) whereas most of the caves don’t have any, so it’s difficult to hunt for specifically in the caves.

Soft Coal

If you’re low on fuel and can’t find enough medium or hard coal to keep up your fuel supply while searching for the other ores you need, this is the best remaining option. It doesn’t give much spark per block mined but it’s plentiful and scattered everywhere across all planets.

If you also need copper/iron, digging out a soft coal vein in an area where you see copper or iron can lead to more ores and give you a bit more value for your time.

If you need a lot of fuel and don’t want anything else, this is probably what you should harvest despite the higher value of the medium and hard coals.

Special mention: Compact Peat

The most efficient furnace fuel if you have it. Each block of compact peat is worth 1.8 soft coal pieces in a spark core, or roughly 2.16 soft coal pieces in a furnace. Mass harvesting peaty soil to turn into Compact Peat is very slow compared to coal harvesting though.

But there are shrines made of metamorphic rock and gleam lanterns that can be found on Munteen (and perhaps other ring worlds) which have 26 compact peat blocks under them. There are usually several in the same area. Digging these up is worthwhile if you know their locations or stumble across them, but if you don’t know of any nearby or they’ve already been looted you’re best off harvesting coal instead.

I hope you found my guide useful and happy coal mining!


Great resource! Thanks for putting this together(:

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A good read, thanks for sharing.
You might want to have look at “compact peaty soil”. It can be found in some pre-fabs and is worth 300 sparks if I remember correctly (not sure about the correct value - it’s been a time since I played last). It’s my main source of sparks.


I have heard about and searched for these prefabs on Munteen but not found them yet - I don’t know how much compact peat they have, if it’s a lot that would probably be very worthwhile once you remember a location and it’s not too far!

Don’t forget though that each block of medium coal you find “by accident” on your travels is worth 416 spark if processed into compact coal, more than a full block of compact peat! So don’t leave those medium coal veins untouched on your travels if you see them!

they have 26 compact peat each. every single time

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I too often farm the prefabs for the Compact Peat, as well as the Gleam Lanterns and Gleam most have. I’d say they each have 15 or so Compact Peat, although not all contain Compact Peat. They’re usually found in groups so it’s not too hard to get a good supply. I find it a decent source of smelting fuel as I usually use 80-90% of my Coal for Spark. They’re also made of decorative Metamorphic and Sedimentary stone. Not sure if they exist on Munteen as I haven’t explored there much. I usually farm them on Nasharil.

Otherwise, thanks for this great info!

Compact peat info added to the table and a special mention in the recommendations!


Given the time you need to gather soft coal, and also the tools you need to spend so you can mine surrounding rock, from here on I’m strongly opinionated towards compact peat. Even just grinding peaty soil is something that is so straight forward and gives such good ROI on time and tools that I can’t absolutely find any reason for mining coal. Except if someone knows locations so rich in coal that you don’t have to dig too much around it :smiley:
Also compact peat below prefabs is god given :smiley: if you know good place, you basically have enormous ROI compared to soft coal. (I can’t say for medium and hard since I haven’t mined much of those)
I managed to gather 540 peaty soil with iron shovel in a bit less than 25 minutes, so that gives me 75 compact peat which is 22500 spark. That’s basically 1000 spark per minute of grinding, if I invest an hour I could get ~60k spark worth of peaty soil. That sounds like pretty good ROI for me :smiley:
I might be wrong, I might just never got to a good coal source, but for now I’m gonna grind only peaty soil for my fuel needs.

As for tools price it is 200 blocks per iron tool, so if you mass craft shovels, you get 1.5 iron per tool, so I spent ~4 iron on 75 compact peat.


Tru that @Spoygg. I was using compact peat as my main spark source myself. Soft coal went all to furnace while whenever I could lay my hand on medium/hard coal I would make compact and put in the core for spark, but sometime (if I was low on fuel in furnace and rich in spark) I would use compact medium coal in furnace as well.


Yeah, that’s my thinking also :slight_smile: I’ll sure get my hands on all coal I can get, but when I need fuel, like now, I’ll do some peaty soil grind, or rob some prefabs :smiley:


prefabs were always my favorite - 20 minutes in 4 of them ruins in one location and I had 100 compact peat; sure it was Munteen and before I was finished with peat there were legions of cuttletrunks waiting outside, but it still beats mining coal by a mile


Hi there !

I made a some math yesterday about coal, and I think this topic, even if it’s old, is the place to submit my calculations to verifications.

Before I start, I must say I’m new to the game, and I did those calculations for entertainment :smile:

Let’s say I have a bunch of Soft Coal and I want to make Compact Soft Coal. To supply the compacter with sparks, I’ll use Soft Coal.

1 Soft Coal (1sc) equals 100 sparks.
1 Compact Soft Coal (1csc) equals 1200 sparks.

Single craft:

10sc give 1csc that to say 1000sparks make 1200sparks. In the process 180sparks are consumed and that represents 1.8sc (let’s say 2). So in reality, I must have 12sc to make 1csc, and 1180sparks gives 1200 sparks, that to say a gain of 20sparks.
That is ridiculously low. 20sparks are 1.7% of 12 Soft Coal.

Bulk craft:

80sc give 10csc that to say 8000sparks make 12000sparks. In the process, 1800sparks are consumed and that represents 18sc. I must have in reality 98sc (9800sparks) to make 10csc (12000sparks), that to say a gain of 2200sparks.
it’s less ridiculous :wink: 2200sparks are 22.4% of 98 Soft Coal.

Mass craft:

360sc give 50csc that to say 36000sparks make 60000sparks. In the process, 9000sparks are consumed and that represents 90sc. I must have 450sc (45000sparks) to make 50csc(60000sparks), that to say a gain of 15000sparks.
15000sparks are 33.3% of 450 Soft Coal.

I still don’t have the possibility to craft it, I must craft power coils (and I don’t know if power coils consume something to produce power). Could you verify my calculations?

All this crafting requires time. In your opinion and experience, does the time past to bulk craft or mass craft Compact Soft Coal values the 22.4% or 33% sparks gain?