Hy`dro·mi'ca noun [ Hydro- , 1 + mica .] (Min.) A variety of potash mica containing water. It is less elastic than ordinary muscovite. Hydromica schist (Min.) , a mica schist characterized by the presence of hydromica. It often has a silky luster and almost soa... Found on http://www.encyclo.co.uk/webster/H/77