nether geodes, cristallized fire

geodes could be in nether as well, objects embeded in netherack
outer layer could be still smooth basalt
middle layer could be however of some different material, made up material to fit in theme of nether which is full of fantasy/made up things, it could be some specific kind of netherack, or calcite, however tinted to gray or red
inside could be again some fantasy crystal so they can be sought for for other purposes than overworld geodes, maybe crystallized fire, same as regular geode, there would be layer of blocks of crystal with some budding version that would grow more individual crystals
if geode would be located in soulsand valley, it could have crystallized soul fire inside instead
crystallized fire crystals and blocks would look similar to their amethyst counterparts but have orange/red color, soul ones blue, slowly pulsating similarly like prismarine do, just faster a bit but still slowly, burn you when you step on them similarly as magma blocks, crystals as well as blocks, they would also make similar tones to amethyst
crystallized fire could be used as renewable fuel source with decent efficiency, about same as coal, regular could smelt 6-8 items and soul one 8-10, or something about those numbers
there could be made other items crafted of crystals same as cut/smooth textures of crystal blocks we should have for amethyst too
geode would give nether another small touch and crystallized fire sounds as interesting fantasy element to have in those instead of regular crystals