| prismatic crystals of minerals, such as lollingite, pyrolusite, eaargite, zincite, millerite and niccolite,...these broad groups-for example, cuprite Cu 20, pyrolusite MnO 2 and naumannite Ag2 Se occur among the sulpho-salts-but...Zinkenite Naumannite Miargyrite Bertbierite Stibnite Pyrolusite Bournonite Jamesonite Hessite Emplectite Chalcostibite... Pyrargyrite 3 4 Covellite Galena 2 2 1 Pyrolusite Stibnite Chalcophanite 4 1 Chalcocite Antimony...Coarsely crystalline material. t Betafite from Madagascar has a mean hardness of 642. isotropic TABLE |
