Tuff in Minecraft is a type of rock made out of volcanic ash, and is only currently used for decor not crafting. It has a grey and uneven texture showing the rough volcanic nature of its creation. Tuff can replace stone, deepslate, granite, or andesite, and polished versions of these blocks.
Where is Tuff found?
Tuff blocks are generated naturally underground in groups of 2, and usually below Y=16 in the Overworld. They are found in blobs, natural ore deposits that are usually discovered in caverns. The Tuff blocks are not flammable, so they do not catch fire in lava, and they have blast resistance 6 which is the same as stone.
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Tuff has a hardness of 1.5 and a base breaking time of 7.5 but does not drop any Tuff if broken down by hand. If mined with a wooden tool such as a pickaxe, the break time is reduced to 1.15 and the block drops Tuff. Even less time is taken to mine the block with other types of pickaxe such as stone (0.6), iron (0.4), diamond (0.3), netherite (0,25), or golden (0.2). Those are break times are based on unenchanted pickaxes or other tools, used by players without any added status effects.