Bedrock Edition:Glowing Obsidian (Item)
Glowing obsidian is an unused block that was formerly generated by the nether reactor. It has never been intended to be obtainable in item form, but there are two known methods of obtaining the item in Survival mode.
Obtaining
Nether reactor
Upon the activation of a nether reactor from v0.5.0 alpha to v0.11.1 alpha, any blocks comprising the nether reactor structure, excluding the nether reactor core, are converted to glowing obsidian. However, mining glowing obsidian with the correct tool drops regular obsidian until beta 1.2.13.5. This means that the player either needs to update to that version or later while the nether reactor is still active to obtain the glowing obsidian item, or instead update to v0.12.1 alpha build 1 or later and mine the glowing obsidian with a Silk Touch-enchanted diamond pickaxe to obtain it in an earlier version.
Falling block transmutation
Glowing obsidian can be obtained via falling block transmutation. This method works from beta 1.16.0.52 to beta 1.16.100.52.