Glow Lichen

Glow Lichens are non-solid blocks, $1/16$ of a block in thickness that can be placed on all the sides of a solid block.

Natural generation
Glow Lichen is naturally generated on stone, andesite, diorite, granite, calcite, tuff and dripstone blocks underground.

Post-generation
bone meal will spread it on a random adjacent block if possible, otherwise bone meal will be wasted. It is possible to cover the sides and the top of an adjacent block by bonemealing one lichen, but not the back. Otherwise, Glow Lichen does not spread naturally.

Breaking
Glow Lichens can be destroyed with anything, but using shears is the only way to collect them. Efficiency on Shears has no effect when used with Glow Lichens.

Light Source
Glow Lichen emit a light level of 7.

Trivia

 * If the player removes all directional states using a debug stick, the block will be invisible but the light emission will remain, unless another block is placed there.
 * In 21w03a, there is a bug that causes Glow Lichens to be waterlogged when placed in lava, making it possible to have water in the Nether.