| Abernathyite | K(UO₂)(AsO₄)·3H₂O | Tetragonal | — | — |
| Achyrophanite | (K,Na)₃(Fe³⁺,Ti,Al,Mg)₅O₂(AsO₄)₅ | Orthorhombic | — | — |
| Adamite | Zn₂AsO₄(OH) | Orthorhombic | 3.5 | 4.23 g/cm³ |
| Adelite | CaMgAsO₄(OH) | Orthorhombic | 5.0 | — |
| Aerugite | Ni₈.₅(AsO₄)₂As⁵⁺O₈ | Trigonal | 4.0 | 5.85 g/cm³ |
| Agardite-(Ce) | CeCu²⁺₆(AsO₄)₃(OH)₆·3H₂O | Hexagonal | 3.0 | — |
| Agardite-(La) | LaCu²⁺₆(AsO₄)₃(OH)₆·3H₂O | Hexagonal | — | — |
| Agardite-(Nd) | NdCu²⁺₆(AsO₄)₃(OH)₆·3H₂O | Hexagonal | — | — |
| Agardite-(Y) | YCu²⁺₆(AsO₄)₃(OH)₆·3H₂O | Hexagonal | — | — |
| Agujaite | Na₆Al₆(H₂O)₁₅(OH)₃(AsO₄)₅(AsO₃OH)₃⋅3H₂O | Trigonal | — | — |
| Akrochordite | Mn²⁺₅(AsO₄)₂(OH)₄·4H₂O | Monoclinic | 3.5 | — |
| Aktashite | Cu₆Hg₃As₄S₁₂ | Trigonal | — | — |
| Alacránite | As₈S₉ | Monoclinic | 1.5 | — |
| Alarsite | AlAsO₄ | Trigonal | — | 3.35 g/cm³ |
| Aleutite | [Cu₅O₂](AsO₄)(VO₄)·(Cu,K,Pb,Rb,Cs,)Cl | Monoclinic | — | — |
| Alexshubnikovite | Ca₂Cu₉(AsO₄)₄(OH)₉Cl(H₂O)₈·2H₂O | Monoclinic | — | — |
| Algodonite | Cu₁₋ₓAsₓ (x ~0.15) | — | — | — |
| Allactite | Mn²⁺₇(AsO₄)₂(OH)₈ | Monoclinic | 4.5 | — |
| Alloclasite | CoAsS | Monoclinic | — | 6.26 g/cm³ |
| Alumoedtollite | K₂NaCu₅AlO₂(AsO₄)₄ | Triclinic | — | — |
| Ambrinoite | [K,(NH₄)]₂(As,Sb)₆(Sb,As)₂S₁₃·H₂O | Triclinic | — | — |
| Anatolyite | Na₆(Ca,Na)(Mg,Fe³⁺)₃Al(AsO₄)₆ | Trigonal | — | — |
| Anduoite | RuAs₂ | Orthorhombic | — | 8.23 g/cm³ |
| Andyrobertsite | KCdCu₅(AsO₄)₄[As(OH)₂O₂]·2H₂O | Monoclinic | 3.0 | 4.01 g/cm³ |
| Angelellite | Fe³⁺₄(AsO₄)₂O₃ | Triclinic | 5.5 | — |
| Annabergite | Ni₃(AsO₄)₂·8H₂O | Monoclinic | — | — |
| Anorpiment | As₂S₃ | Triclinic | — | — |
| Anorthoroselite | Ca₂Co(AsO₄)₂·2H₂O | Triclinic | — | — |
| Arakiite | ZnMn²⁺₁₂Fe³⁺₂(As³⁺O₃)(As⁵⁺O₄)₂(OH)₂₃ | Monoclinic | — | — |
| Argentobaumhauerite | Ag₁.₅Pb₂₂As₃₃.₅S₇₂ | Monoclinic | 3.0 | — |
| Argentoliveingite | AgxPb₄₀-₂xAs₄₈+xS₁₁₂ | Triclinic | — | — |
| Argentopearceite | Ag₁₆As₂S₁₁ | Trigonal | — | — |
| Argentotennantite-(Fe) | Ag₆(Cu₄Fe₂)As₄S₁₂S | Cubic | — | — |
| Argentotennantite-(Zn) | Ag₆Cu₄(Fe,Zn)₂As₄S₁₃ | Cubic | — | — |
| Armangite | Mn²⁺₂₆As³⁺₁₈O₅₀(CO₃)(OH)₄ | Trigonal | — | — |
| Armellinoite-(Ce) | Ca₄Ce₄+(AsO₄)₄·H₂O | Tetragonal | — | — |
| Arsenatrotitanite | NaTi(AsO₄)O | Monoclinic | — | 3.72 g/cm³ |
| Arsenbrackebuschite | Pb₂Fe³⁺(AsO₄)₂(OH) | Monoclinic | — | — |
| Arsenic (native) | As | Trigonal | 3.5 | 5.68 g/cm³ |
| Arseniopleite | (Ca,Na)NaMn²⁺(Mn²⁺,Mg,Fe²⁺)₂(AsO₄)₃ | Monoclinic | — | — |
| Arseniosiderite | Ca₂Fe³⁺₃O₂(AsO₄)₃(H₂O)₂·H₂O | Monoclinic | 4.5 | — |
| Arsenmedaite | Mn²⁺₆ As₅+Si₅O₁₈(OH) | Monoclinic | — | — |
| Arsenobenauite | SrFe³⁺₃(AsO₄)(AsO₃OH)(OH)₆ | Trigonal | — | — |
| Arsenocrandallite | CaAl₃(AsO₄)(AsO₃OH)(OH)₆ | Trigonal | — | — |
| Arsenoflorencite-(Ce) | CeAl₃(AsO₄)₂(OH)₆ | Trigonal | — | — |
| Arsenoflorencite-(La) | LaAl₃(AsO₄)₂(OH)₆ | Trigonal | — | — |
| Arsenoflorencite-(Nd) | NdAl₃(AsO₄)₂(OH)₆ | — | — | — |
| Arsenogorceixite | BaAl₃(AsO₄)(AsO₃OH)(OH)₆ | Trigonal | — | — |
| Arsenogoyazite | SrAl₃(AsO₄)(AsO₃OH)(OH)₆ | Trigonal | — | — |
| Arsenohauchecornite | Ni₁₈Bi₃AsS₁₆ | Tetragonal | — | — |
| Arsenohopeite | Zn₃(AsO₄)₂·4H₂O | Orthorhombic | 3.0 | 3.42 g/cm³ |
| Arsenolamprite | As | Orthorhombic | 2.0 | — |
| Arsenolite | As₂O₃ | Cubic | 1.5 | — |
| Arsenopalladinite | Pd₈As₃ | Triclinic | 4.0 | 10.40 g/cm³ |
| Arsenopyrite | FeAsS | Monoclinic | — | 6.35 g/cm³ |
| Arsenovanmeersscheite | U(UO₂)₃(AsO₄)₂(OH)₆·4H₂O | Orthorhombic | — | — |
| Arsenowagnerite | Mg₂(AsO₄)F | Monoclinic | — | — |
| Arsenoústalečite | (Cu₄Cu₂)(Cu₄Cu⁺₂)(As₂Te₂)Se₁₂Se | Cubic | — | — |
| Arsenquatrandorite | Ag₁₇.₆Pb₁₂.₈Sb₃₈.₁As₁₁.₅S₉₆ | Monoclinic | — | — |
| Arsenudinaite | NaMg₄(AsO₄)₃ | Tetragonal | — | 3.83 g/cm³ |