Hmm, you learn something new every day. Shungite. I guess the game steers away from real-geographical location coined references but since it sounds plausable as it is maybe it'd be fine to get away with it. We have Kaolinite after all.
Anti-bacterial properties
Also a property shared between silver, which to say perhaps if water is collected and deposited into a silver metal barrel/shungite pot, it will not eventually over time become stagnant if left alone unlike alcohol. But that's a feature that doesn't exist but feasibly be introduced.
Water filtration (We got screw pumps for that, ya know!)
Maybe a layer of Shungite designated as a aquifer could sanitize salt-water natively, since coastal areas and saltwater swamps are very common for having sedimentary rocks where Shungite occurs.
Materially Shungite is brittle stone, so has a lot in common with obsidian's kind of native strength to snap besides sharpness and occurs in sedimentary rocks in 'clasts' like other stones within their non-mineral 'veins' like kimberlite within igneous layers.
Pigment (Bah! Just go and get yerself some sliver barb!)
Silver barb can easily be regrown though if your fortress lays within a appropriate evil biome, depending on the amount of imported or native Shungite it'd be a limited commodity for the desirable color.
All and all a good suggestion.