Arsenic Minerals Chemical formula Source Reference Native arsenic As Hydrothermal veins. [1] Niccolite NiAs Vein deposits and norites. [1] Realgar AsS Vein deposits, often associated with orpiment, clays andlimestones, also deposits from hot springs. [1] Orpiment As2S3 Hydrothermal  veins,  hot  springs,  volcanic  sublimationproducts. [1] Cobaltite CoAsS High temperature deposits, metamorphic rocks. [1] Arsenopyrite FeAsS The  most  abundant  As  mineral,  dominantly  in  mineral veins. [1] Tennantite (Cu,Fe)12As4S13 Hydrothermal veins. [1] Enargite Cu3AsS4 Hydrothermal veins. [1] Arsenolite As2O3 Secondary mineral formed by oxidation of arsenopyritenative arsenic and other As minerals. [1] Clauderite As2O3 Secondary  mineral  formed  by  oxidation  of  realgararsenopyrite and other As minerals. [1] Scorodite FeAsO4•2H2O Secondary mineral. [1] Anabergite (Ni,Co)3(AsO4)2•8H2O Secondary mineral. [1] Hoernesite Mg3(AsO4)2•8H2O Secondary mineral, smelter wastes. [1] Haematolite (Mn,Mg)4Al(AsO4)(OH)8 Secondary mineral. [1] Conichalcite CaCu(AsO4)(OH) Secondary mineral. [1] Pharmacosiderite Fe3(AsO4)2(OH)3•5H2O Oxidation product of arsenopyrite and other As minerals. [1] Materials Concentration As (mg/kg) Process   Igneous material   Cooling and solidification of magma or lava. [26] Basalt <1-113   [26] Ultrabasics <1-16   [26] Granites <1-15   [26] Sedimentary material   Formed  by  the  deposition  of  material  (organic  and/orminerals) at the Earth's surface and within bodies of water. [26] Shales and clays <1-500   [26] Sandstones <1-120   [26] Limestones <1-20   [26] Phosphorites 3-100   [26]

Table 1: Arsenic sources and concentrations in earth materials; adopted and modified from [1,26,27].