Hanging wall - The overlying side of an orebody, fault, or mine working, esp. the wall rock above an inclined vein or fault.

 

Hexavalent Chromium - Compounds which contain the element chromium in the +6 oxidation state. They are used as corrosion inhibitors, however due to their toxicity they are being replaced by alternatives. Hexavalent chromium is recognised as a human carcinogen.

 

Host Rock - Body of rock serving as a host for other rocks or for mineral deposits; e.g., a pluton containing xenoliths, or any rock in which ore deposits occur. It is a somewhat more specific term than country rock.