Ancient Debris

Ancient debris is a rare ore found in the Nether, and is the only source of netherite scrap. It floats on lava in item form and it cannot be burned. It also has an extremely high blast resistance, meaning it cannot be blown up.

Mineral veins
Ancient debris generate in the Nether in the form of mineral veins. Two veins generate per chunk: one vein of 1–3 ancient debris generates with a periodic Gaussian distribution (similarly to lapis lazuli ore) between levels 8–22, and an additional vein of 1–2 ancient debris generates randomly between levels 8–119. There is an average of 1.7 ancient debris blocks per chunk, with a maximum of 5. Ancient debris never generates exposed to air.

Obtaining
Ancient debris drops as an item if mined by a diamond pickaxe or better. If mined by any other tool, it drops nothing.

Method video https://m.youtube.com/watch?v=Gp8h0TWH-ig

Trivia

 * Ancient debris and blocks of netherite are the only blast-resistant blocks that are also moveable by pistons.
 * These two blocks are also two of only three blocks that require at least a diamond pickaxe to mine, the other being obsidian.
 * Ancient debris, along with nether quartz, are the only two ores that can be found only in the Nether.
 * It is the most blast-resistant of all the ores in the game.
 * Its blast resistance is tied with obsidian.
 * It is the only ore in the game to not have the name of the mineral obtained from it or the word "ore" in its name.
 * It is also one of only two ores in which its name is not based on a real-life mineral, the other being redstone ore.
 * It is one of the 3 ores that drops itself when mined with a non-Silk Touch pickaxe, the others being iron ore and gold ore.
 * Despite the rarity, it's actually considered the 2nd rarest ore in the game, second only to emerald ore.