Non-silicate Mineral Groups
Non-silicate minerals, though less abundant than silicates, include most ore minerals and important rock-forming carbonates, oxides, and sulfates.
Definition
The mineral classes whose anion or anionic group is something other than the silicon-oxygen tetrahedron, encompassing native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates.
Scope
This topic covers the major non-silicate classes defined by anion or anionic complex: native elements (gold, copper, diamond, graphite), sulfides and sulfosalts (pyrite, galena, chalcopyrite), oxides and hydroxides (hematite, magnetite, corundum), halides (halite, fluorite), carbonates (calcite, dolomite), sulfates (gypsum, barite), and phosphates (apatite). It emphasizes their structures, occurrences, and economic significance.
Core questions
- How are non-silicate minerals divided into chemical classes?
- Why do sulfides and oxides constitute most metallic ore minerals?
- What structural features distinguish calcite from aragonite?
- How do native elements bond differently from ionic mineral groups?
Key theories
- Anion-based classification of non-silicates
- Non-silicate minerals are grouped by their dominant anion or anionic complex (sulfide, oxide, carbonate, sulfate, phosphate, halide), each class sharing characteristic bonding, structure, and physical properties.
- Polymorphism in carbonates and oxides
- Several non-silicate compositions crystallize in more than one structure depending on conditions, as in the calcite-aragonite pair for calcium carbonate, illustrating the structural control of pressure and temperature.
Clinical relevance
Non-silicate minerals are the principal sources of metals, industrial minerals, and gemstones; carbonates build major sedimentary formations and reefs; and oxides such as magnetite record the magnetic history of rocks used in paleomagnetism.
History
The chemical grouping of ore and non-silicate minerals was systematized in Dana's System of Mineralogy and refined through detailed structural studies in the twentieth century, which clarified the relationships among sulfides, oxides, and the carbonate polymorphs.
Key figures
- James Dwight Dana
- Cornelis Klein
- Hugo Strunz
Related topics
Seminal works
- klein2007
- dana1997
Frequently asked questions
- Are diamond and graphite the same mineral?
- They are two distinct minerals with identical composition (carbon) but different structures, a classic example of polymorphism; diamond is the densest, hardest form and graphite the soft, layered form.
- Why are most ores non-silicate minerals?
- Metals are most economically concentrated as sulfides and oxides, where they form simple, often dense compounds that are easier to smelt than the metals dispersed within silicate structures.