What exactly is done to classify minerals in Earth Sciences such as Geology? How can it be known if one mineral is the same as another if they should be visually different?
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2 Answers
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Minerals are defined by chemical composition and crystallography. Dana classification scheme or new Dana classification scheme divides known mineral species in eight broad groups based on primary chemical properties and crystal form.
Organic vs inorganic
Silicates vs non-silicates
Subdivided silicates into smaller groups by crystalline structures
Metals vs non-metals
Subdivide non-metals into smaller groups
metal oxides
metal sulfides
metal and non-metal acid salts organized by dominant anion (1)(2)
(1) In chemistry, a salt is an ionic compound that can be formed by the neutralization reaction of an acid and a base.1 Salts are composed of related numbers of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge). These component ions can be inorganic, such as chloride (Cl−), or organic, such as acetate (CH3CO−2.); and can be monatomic, such as fluoride (F−), or polyatomic, such as sulfate (SO2−4). (from wikipedia)
(2) Some of these subgroups represent hypothetical acid-base reactions not actually seen in nature but modeled after known acid-base reactions. My opinion here is that this approach was used because it was a popular theory in chemistry at the time when James Dwight Dana published his work in 1837.
There are other minerals classification systems:
By crystal system -triclinic, monoclinic, orthorhombic, tetragonal, hexagonal, and cubic.
By Cleavage, parting, fracture, and tenacity
By mineral hardness
By specific gravity or density
By mineral association (my favorite and often the best way of identifying an unknown mineral especially when the location is known.
answered Feb 18, 2019 at 13:32
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Minerals are classified as follows: Native elements, Sulphides, Sulphosalts, Oxides, Halides, Carbonates, Nitrates, Borates, Phosphates, Sulphates, Tungstates, Silicates I have listed some of the things I know for more details on the classification of minerals follow this [link].1
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$\begingroup$ There is Dana classification webmineral.com/danaclass.shtml#.XGqcH2N7lnI and Strunz classification webmineral.com/strunz.shtml#.XGqcVmN7lnI, but mainly allbody accepts with little differences the british encyclopedia list linked by Arsath $\endgroup$– user12525Commented Feb 18, 2019 at 11:52