adamantine adularia aenigmatite alps armalcolite axinite ball-and-stick model betafite borate brazil brookite carbonate clay crystal crystal habit euxenite feldspar gneiss granite greek language haggertyite heavy mineral sands ore deposits hibonite ilmenite keilhauite list of minerals lorenzenite melanite mica mineral mohs scale of mineral hardness nenadkevichite oxide perovskite polycrase public domain rutile sabinaite sandstone schist sedimentary rock silicate slate specific gravity switzerland tetragonal crystal system titanite titanium titanium dioxide valais warwickite wikimedia commons xenotime zimbabweite zirconolite zircophyllite zirkelite