It looks to me as though it's a fairly well crystallized metamorphosed sedimentary rock of some description, so I guess it'd be fairly inert. But you could do the acid test for carbonate minerals just to make sure; it'll effervesce if any are present, which'll be a sure sign it'll raise TDS. Dilute hydrochloric acid is best, but good old vinegar will do. But I suppose it'd be too late then since you would've had to buy it🙄
Having said that though most of us don't bat an eyelid at using seiryu stone which, in its various guises, is just limestone somewhere along the metamorphic continuum. It usually raises TDS especially in high-tech tanks, but frequent water changes usually keep this in check.