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Back to: Mr. Butler's Home Page Earth Science Page HES Home Page Word Document: "Mineral Groups" "Mineral Groups" Lecture Notes Most minerals are ionic compounds. Minerals are classed by the negative ion [the non-metallic "right" side of the chemical compound symbol: i.e. NaCl] It seems the negative ion imparts important chemical properties to minerals... so minerals with similar non-metals are classed together. By far the largest mineral group is the silicates. All other mineral groups are called non-silicates. [Something like aluminum silicate or iron silicate would be members of the silicates, if they occur naturally.] (metal = +ION) (non-metal "side" = -ION) The -ate ending represents oxygen. Iron silicate > >>> FeSiO4 { iron, silicon, oxygen (metal) + (silicon, oxygen) >>>
The -ide ending of a compound name indicates all elements in the compound are named. For example: Iron sulfide >>> FeS { iron and sulfur only}* (metal) *[chemical formulae above is simplified, not balanced] These are five common non-silicate groups with their Key Elements: carbonates metal + carbon and oxygen sulfates metal + sulfur and oxygen sulfides metal + sulfur oxides metal + oxygen halide metal + a HALOGEN (F, Cl, …. : Family #17 elements) The silicate tetrahedron give the silicates similar properties. Silicate Tetrahedron
Iron Silicate (+) ( -) [note: This “molecule” is a simplification; the chemical formula is not balanced.]
Quartz is a unique silicate with no metal ion! [SiO2] Quartz is very strong because its structure is exclusively Silicon-oxygen tetrahedral, which fit together “perfectly” and thus have very strong covalent bonding in all directions. This is why it fractures rather than cleaves, there are no weak bonding planes. It breaks between randomly located impurities, which were incorporated into the crystalline lattice during formation.
Stenography and graphics by JS
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