| Abellaite | NaPb₂(CO₃)₂(OH) | Trigonal | — | — |
| Abelloemringerite | Cu₂Pb₂Mn³⁺Mn⁴⁺₃O₁₁(OH)(H₂O)₂·H₂O | Orthorhombic | — | — |
| Abelsonite | NiC₃₁H₃₂N₄ | Triclinic | 2.5 | — |
| Abernathyite | K(UO₂)(AsO₄)·3H₂O | Tetragonal | — | — |
| Abhurite | Sn²⁺₂₁O₆(OH)₁₄Cl₁₆ | Trigonal | 2.0 | — |
| Acmonidesite | (NH₄,K,Pb)₈NaFe²⁺₄(SO₄)₅Cl₈ | Orthorhombic | — | — |
| Actinolite | Ca₂(Mg,Fe)₅[OH|Si₄O₁₁]₂ | Monoclinic | — | — |
| Acuminite | SrAlF₄(OH)·H₂O | Monoclinic | 3.5 | — |
| Adachiite | CaFe²⁺₃Al₆(Si₅AlO₁₈)(BO₃)₃(OH)₃(OH) | Trigonal | 7.0 | — |
| Adamite | Zn₂AsO₄(OH) | Orthorhombic | 3.5 | 4.23 g/cm³ |
| Adamsite-(Y) | NaY(CO₃)₂·6H₂O | Triclinic | 3.0 | — |
| Adelite | CaMgAsO₄(OH) | Orthorhombic | 5.0 | — |
| Admontite | MgB₆O₁₀·7H₂O | Monoclinic | — | — |
| Adolfpateraite | K(UO₂)(SO₄)(OH)(H₂O) | Monoclinic | — | — |
| Adranosite | (NH₄)₄NaAl₂(SO₄)₄Cl(OH)₂ | Tetragonal | — | — |
| Adranosite-(Fe) | (NH₄)₄NaFe₂(SO₄)₄Cl(OH)₂ | Tetragonal | — | — |
| Aerinite | (Ca,Na)₆(Fe³⁺,Fe²⁺,Mg,Al)₄(Al,Mg)₆Si₁₂O₃₆(OH)₁₂(CO₃)·12H₂O | — | 3.0 | 2.48 g/cm³ |
| Afmite | Al₃(OH)₄(H₂O)₃(PO₄)(PO₃OH)·H₂O | Triclinic | — | — |
| Afwillite | Ca₃[SiO₃(OH)]₂·2H₂O | Monoclinic | — | — |
| Agaite | Pb₃Cu²⁺Te⁶⁺O₅(OH)₂(CO₃) | Orthorhombic | — | — |
| 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 | — | — |
| Agrinierite | K₂Ca[(UO₂)₃O₃(OH)₂]₂·5H₂O | Orthorhombic | — | — |
| Agujaite | Na₆Al₆(H₂O)₁₅(OH)₃(AsO₄)₅(AsO₃OH)₃⋅3H₂O | Trigonal | — | — |
| Aheylite | Fe²⁺Al₆(PO₄)₄(OH)₈·4H₂O | Triclinic | — | — |
| Ahlfeldite | NiSeO₃·2H₂O | Monoclinic | — | — |
| Ajoite | K₃Cu²⁺₂₀Al₃Si₂₉O₇₆(OH)₁₆·8H₂O | Triclinic | — | — |
| Akaganeite | (Fe³⁺,Ni²⁺)₈(OH,O)₁₆Cl₁.₂₅·nH₂O | Monoclinic | — | — |
| Akasakaite-(Ce) | (CaCe)(AlAlMn²⁺)O[Si₂O₇][SiO₄](OH) | Monoclinic | — | — |
| Akasakaite-(La) | (CaLa)(AlAlMn²⁺)O[Si₂O₇][SiO₄](OH) | Monoclinic | — | — |
| Akatoreite | Mn²⁺₉Al₂Si₈O₂₄(OH)₈ | Triclinic | 6.0 | — |
| Akdalaite | Al₅O₇(OH) | Hexagonal | — | — |
| Aklimaite | Ca₄[Si₂O₅(OH)₂](OH)₄·5H₂O | Monoclinic | — | — |
| Akopovaite | Al₄Li₂(OH)₁₂(CO₃)(H₂O)₃ | Monoclinic | — | — |
| Akrochordite | Mn²⁺₅(AsO₄)₂(OH)₄·4H₂O | Monoclinic | 3.5 | — |
| Aksaite | MgB₆O₇(OH)₆·2H₂O | Orthorhombic | — | — |
| Albertiniite | Fe²⁺(SO₃)·3H₂O | Monoclinic | — | — |
| Albrechtschraufite | MgCa₄F₂[UO₂(CO₃)₃]₂·17-18H₂O | Triclinic | 2.8 | 2.60 g/cm³ |
| Alcaparrosaite | K₃Ti⁴⁺Fe³⁺(SO₄)₄O(H₂O)₂ | Monoclinic | — | — |
| Aldermanite | Mg₅Al₁₂(PO₄)₈(OH)₂₂·32H₂O | Orthorhombic | 2.0 | — |
| Aldridgeite | (Cd,Ca)(Cu,Zn)₄(SO₄)₂(OH)₆·3H₂O | Monoclinic | — | — |
| Alexkhomyakovite | K₆(Ca₂Na)(CO₃)₅Cl·6H₂O | Hexagonal | — | — |
| Alexshubnikovite | Ca₂Cu₉(AsO₄)₄(OH)₉Cl(H₂O)₈·2H₂O | Monoclinic | — | — |
| Alflarsenite | NaCa₂Be₃Si₄O₁₃(OH)·2H₂O | Monoclinic | — | — |
| Alfredopetrovite | Al₂(Se⁴⁺O₃)₃·6H₂O | Hexagonal | 2.5 | — |
| Alfredstelznerite | Ca₄(H₂O)₄[B₄O₄(OH)₆]₄(H₂O)₁₅ | Orthorhombic | — | — |
| Alicewilsonite-(YLa) | Na₂Sr₂YLa(CO₃)₆·3H₂O | Triclinic | — | — |
| Aliettite | Ca₀.₂Mg₆(Si,Al)₈O₂₀(OH)₄·4H₂O | Monoclinic | — | — |
| Allactite | Mn²⁺₇(AsO₄)₂(OH)₈ | Monoclinic | 4.5 | — |
| Allanite-(Ce) | CaCe(Al₂Fe²⁺)[Si₂O₇][SiO₄]O(OH) | Monoclinic | — | — |
| Allanite-(La) | CaLa(Al₂Fe²⁺)[Si₂O₇][SiO₄]O(OH) | Monoclinic | — | — |
| Allanite-(Nd) | CaNd(Al₂Fe²⁺)[Si₂O₇][SiO₄]O(OH) | Monoclinic | — | — |
| Allanite-(Sm) | (CaSm)(AlAlFe²⁺)O[Si₂O₇][SiO₄](OH) | Monoclinic | — | — |
| Allanite-(Y) | {CaY}{Al₂Fe²⁺}(Si₂O₇)(SiO₄)O(OH) | Monoclinic | — | — |
| Allanpringite | Fe³⁺₃(PO₄)₂(OH)₃·5H₂O | Monoclinic | 3.0 | — |
| Alleghanyite | Mn²⁺₅(SiO₄)₂(OH)₂ | Monoclinic | — | — |
| Allophane | Al₂O₃(SiO₂)₁.₃-₂.₀·2.5-3.0H₂O | — | 3.0 | — |
| Alloriite | (Na,K,Ca)₂₄(Na,Ca)₄Ca₄(Si,Al)₄₈O₉₆(SO₄)₄(SO₃,CO₃)₂(OH,Cl)₂(H₂O,OH)₄ | Trigonal | — | — |