This is not a single block, but if you have too much building material and need inspiration on how to use them up - explore the most inefficient house ever .
The house consists of only 200 blocks, but took 1,280 blocks to construct.
The architect went insane, shortly after completing it.
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Ice, it can only be formed in a winter biome, must be moulded and cannot be made if there is a roof above it.
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I'm leaning towards, for the time consuming side, Diamond Blocks .
Nine diamonds per block, and combined with their rarity, you could be mining a very, very long time just to build a wall...
Gold blocks might be up there too, but I'm not as sure on that one.
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Glowstone
It requires a lot of effort just to build an obsidian portal and get to the nether.
Once there, it's extremely dangerous, you will almost certainly die at least once.
You need to collect a lot of glowstone, which due to its location is difficult to get to, just to make a small number of blocks.
I reckon that starting a fresh game, it would take you longer to build a glowstone house (of say a hundred blocks) than a house from any other block, and you would die more times.
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On the labour intensive and time consuming I see two contenders: Obsidian .
Simply on the amount of time it takes to mine and the fact you need a diamond pickaxe to mine it.
You can create obsidian in place using lava and water but that's time consuming as well - mining iron to make buckets, finding the lava source, transporting it to the building site then dousing it with water.
Bricks .
You have to find the clay (which is fairly rare), bake it into brick and then craft the individual bricks into blocks.
Less so after 1.8 when clay was made more common.
I think the winner is obsidian.
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Cake!
OK, probably not.
But it's at least as intensive as bookshelves, and the thought of making a house out of (essentially) gingerbread is kind of hilarious.
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Bookshelves!
The amount of time spent having to harvest reeds to make paper to make books to make bookshelves means its very exotic/extravagant.
Also: Diamond/gold blocks, 9 diamond/gold to make one block means its very hard to get.
Not to mention the fact that both are super useful.
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I'm not a minecraft player, but I'm going to suggest the "obvious" answer: Obsidian
It's rare to find naturally, it only occurs where water is pouring on to lava.
This means naturally occurring instances are usually over a lava pool, so mining them is fun.
You can, however, create your own obsidian by forcing water to pour on to lava, but this will destroy the lava source in the process (and thus, you need 1 lava source to create 1 obsidian block).
It can only be mined with a Diamond pickaxe and takes a whole 15 seconds per block to mine this way.
It can be removed with other tools, taking 50 seconds per block, but you won't get the obsidian to build with that way.
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In Minecraft, which blocks are the rarest, most expensive to build a house from? In particular, by the following criteria:   Which are the most labour-intensive and time-consuming per block?  Which are the rarest per-block?  Which block is the most dangerous to acquire and build with?
What is the most extravagant building material in Minecraft?
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<minecraft-java-edition>
gaming.stackexchange.com/questions/29273
gaming.stackexchange.com/users/3454/Joe Dovahkiin
Ice can only be formed in a winter biome, diamond blocks, glowstone and obisidian are only very labour intensive and time consuming. It is suggested that Ice, Diamond, Glowstone, Obsidian, Bricks and Bookshelves are the most extravagant and expensive blocks.
Ice, Diamond, Glowstone, Bricks, Obsidian and Bookshelves are the most expensive.