There are many different sources in Genshin Impact, and some are harder to find than others. Noctilucous Jade is an important but rare resource that you will need for certain ascents of weapons and characters.
Noctilucous Jade is found only in the Liyue area and often appears in caves near the village of Mingyun. Like other ores, you will have to break it with your weapon and then collect the pieces that fall. Searching around south of Wuwang Hill and Stone Gate should provide you with a lot of this resource.
The village of Mingyun on the eastern side of Liyue near Dragonspine is the best place to grow it, as it can grow there in several clusters, allowing a large amount of material to be obtained quickly and easily.
The ore will look like a blue crystal, which is used to the ground with black dirt and is quite easily visible due to its size. If you have great trouble finding in the wild, you can visit Shitou, a merchant in the port of Liyue. Sells Iron Chunks, White Iron Chunks and Noctilucous Jade. Nectilucous Jade will cost 1000 Mora each.
A merchant is certainly the easiest way to get this resource, but if you have little Mora or don’t want to spend it every day, you’ll have to look for it in different caves.