Glowstone blob

Glowstone blobs (also known as the glowstone clusters) generate on the underside of terrain blocks in the Nether.

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These are typically veins of glowstone that can be among the hardest natural materials to harvest that don't require digging. They form in coral-like structures on the underside of hanging Netherrack, so they are often found on the ceilings of the Nether, where they provide light along with the ever-present lava.

Glowstone blobs consist of one block-wide tendrils extending from a central clump. Being found in caves, hanging above an ocean of lava and even within nether fortresses, they are the main source of charges of glowstone for respawn anchors.