To find the Jadeplume Terrorshroom, you will have to head to the northwest corner of Sumeru, but in order to get to it you will have to unlock the nearby Statue of Seven and when it is unlocked, you will have to go to the location of the Jadeplume Terrorshroom > look for a portal, which will lead you to its hidden underground location.
The portal is near the Jadeplume Terrorshroom location and when you get there you will have to face the boss, to get your hands on the rewards, among which you might find Nagadus Emerald Chunks.
You can also obtain this material through crafting. To do this you will have to use 3 Nagadus Emerald Chunks and spend 900 Mora, which will allow you to get a single piece of Nagadus Emerald. But keep in mind that the usually won't be enough to get enough of this material. That's all you need to know about where to find Nagadus Emerald Chunks in Genshin Impact, so now that we're done, we hope we've been as helpful as possible, so that you can get your hands on this material as soon as possible.