Sulfate mineral
Minerals containing the sulfate ion, common in evaporites and hydrothermal settings.
Sulfate minerals constitute a mineral class defined by the presence of the sulfate ion (SO₄²⁻) within their crystalline structure. They are most commonly encountered in three principal geological settings: as primary minerals in evaporite deposits formed from the desiccation of ancient water bodies, as gangue (non-valuable) minerals within hydrothermal veins, and as secondary minerals that develop in the oxidizing zone where sulfide mineral deposits are weathered. Due to structural similarities, chromate and manganate minerals are frequently classified alongside sulfates in mineralogical systems. The group encompasses a wide variety of species, including anhydrous sulfates such as barite (BaSO₄), celestite (SrSO₄), anglesite (PbSO₄), and anhydrite (CaSO₄), as well as the rare hanksite (Na₂₂K(SO₄)₉(CO₃)₂Cl), which is notable for combining both sulfate and carbonate ions. Hydrous and hydroxide-bearing sulfates are also abundant, with gypsum (CaSO₄·2H₂O) being one of the most familiar. Other examples include the copper sulfates chalcanthite (CuSO₄·5H₂O) and antlerite (Cu₃SO₄(OH)₄), the magnesium sulfate series from kieserite (MgSO₄·H₂O) through epsomite (MgSO₄·7H₂O) to meridianiite (MgSO₄·11H₂O), and the iron sulfate melanterite (FeSO₄·7H₂O). The alunite group, represented by alunite (KAl₃(SO₄)₂(OH)₆) and jarosite (KFe₃(SO₄)₂(OH)₆), features additional hydroxide anions. The classification of these minerals follows the Nickel–Strunz system, with sulfates, selenates, and tellurates grouped together. This system further subdivides them based on the presence of additional anions, water molecules, and the size of the cations involved, ranging from medium-sized to large cations, and includes categories for both anhydrous and hydrated species.
- class
- Sulfates, selenates, tellurates
- includes
- Anhydrous sulfates, hydroxide and hydrous sulfates, chromates
- common_occurrence
- Evaporite deposits, hydrothermal veins, oxidizing zone of sulfide deposits
- classification_system
- Nickel–Strunz (class 07) and IMA-CNMNC hierarchical scheme
- notable_minerals
- Barite, Gypsum, Chalcanthite, Epsomite, Alunite, Jarosite
Lore & Background
The sulfate minerals are a class of minerals whose crystal structures incorporate the sulfate ion (SO₄²⁻). Their appearance is highly variable, encompassing both anhydrous forms such as barite, celestite, anglesite, and anhydrite, and hydrated or hydroxide-bearing species like gypsum, chalcanthite, epsomite, melanterite, antlerite, brochantite, alunite, and jarosite. Notable for its rarity, hanksite is a mineral that simultaneously contains both sulfate and carbonate groups. These minerals are found in several distinct geological settings. They occur commonly as primary deposits in evaporite environments, where salts crystallize from concentrated brines. They also appear as gangue minerals—non-valuable materials accompanying ore—within hydrothermal veins. Additionally, they form as secondary minerals in the oxidizing zone of sulfide mineral deposits, where sulfides weather and alter. The defining characteristic of the group is the sulfate ion, but the classification also includes structurally similar chromate and manganate minerals. The Nickel–Strunz system organizes these minerals into detailed divisions based on the presence or absence of additional anions and water molecules. Subdivisions include anhydrous sulfates without water, those with additional anions but no water, hydrated sulfates without additional anions, and hydrated sulfates with additional anions, each further sorted by the size of the constituent cations.
Reader's Guide
Sulfate minerals are significant in mineralogy and economic geology due to their widespread occurrence and varied compositions. They include common minerals such as gypsum (CaSO₄·2H₂O), used in construction and plaster, and barite (BaSO₄), a major source of barium. The classification system for sulfates, as outlined in the Nickel–Strunz scheme, provides a hierarchical framework that groups minerals by their chemical and structural properties, including the presence of additional anions or water. This system also incorporates chromates and manganates due to their structural similarity. The IMA-CNMNC has proposed a new hierarchical scheme to refine this classification, reflecting ongoing developments in mineral taxonomy. Sulfate minerals are also important in environmental studies, as they can form in oxidizing zones of sulfide deposits, influencing acid mine drainage and secondary mineral formation.
Did You Know?
- Sulfate minerals include both anhydrous forms like barite and hydrous forms like gypsum.
- The chromate and manganate minerals have a similar structure and are often included with the sulfates in classification systems.
- The Nickel–Strunz classification for sulfates includes classes for uranyl sulfates and thiosulfates.
- Meridianiite (MgSO₄·11H₂O) is a hydrous sulfate mineral listed in the source.
More in Minerals & Ore Deposits 1-24
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record