Isinglass

1. A semitransparent, whitish, and very pure form of gelatin, chiefly prepared from the sounds or air bladders of various species of sturgeons (as the Acipenser huso) found in the rivers of Western Russia. It used for making jellies, as a clarifier, etc. Cheaper forms of gelatin are not unfrequently so called. Called also fish glue.
2. (Min.) A popular name for mica, especially when in thin sheets.