Statistical subdivision by crystal system and classes - 31 December 2017

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Marco E. Ciriotti
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Statistical subdivision by crystal system and classes - 31 December 2017

Messaggio da Marco E. Ciriotti » lun 09 apr, 2018 15:50

A tutto il 31 dicembre 2017 la suddivisione per singonia delle 5340 valide specie minerali è la seguente:

Cubic [cub] 8.78% 469
Hexagonal [hex] 7.55% 403
Monoclinic [mon] 34.48% 1841
Orthorombic [orth] 19.89% 1062
Tetragonal (Quadratic) [tet] 6.78% 362
Triclinic (Anorthic) [tric] 10.56% 564
Trigonal (Rhombohedral) [trig] 11.16% 596
Non-crystalline [nox] 0.47% 25
Decagonal [dec] 0.02% 1
Icosahedric [ico] 0.04% 2
Unknowm crystal system [(!)] 0.28% 15

Total 100.00% 5340

For what reason do monoclinic and orthorhombic systems together (2903) constitute more than half of the total of existing minerals?
Marco E. Ciriotti

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Marco E. Ciriotti
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Re: Statistical subdivision by crystal system and classes - 31 December 2017

Messaggio da Marco E. Ciriotti » lun 09 apr, 2018 17:16

For what reason do monoclinic and orthorhombic systems together constitute more than half of the total of existing minerals?
I try to do a "hint-reply" (most likely unsatisfactory) to the above question.

In the orthorhombic crystal system, all types of centered lattices are possible: P (primitive); I (internally centered = body centered); C (base centetred, but also A and B, that is centered on the a-b, b-c, a-c faces, respectively); F (all faces centered).
We cannot define an orthorhomic lattice as FCC (Face Centered Cubic) because this term implies the cubic metrics (a = b = c; alpha = beta = gamma = 90*). However, in the orthorhombic we can have an F lattice (but not FCC!).
The reason for having all possible types of lattice in the orthorhombic (and not in any other crystal system) stems from the metrics of this system with three different axial values (a,b,c) but all three axial angles equal to 90°.
Monoclinic system differs from orthorhombic only by the beta angle which normally is more than 90° (but it can be also 90°!).
Marco E. Ciriotti

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Marco E. Ciriotti
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Re: Statistical subdivision by crystal system and classes - 31 December 2017

Messaggio da Marco E. Ciriotti » mar 10 apr, 2018 15:19

La suddivisione per classi alla data del 31/12/2017.

Elements 156 2.92%
Sulfides and sulfosalts 762 14.27%
Halides 230 4.31%
Oxides 741 13.88%
Carbonates (+ nitrates) 266 4.98%
Borates 156 2.92%
Sulfates etc. 496 9.29%
Phoshates, arsenates, vanadates 1021 19.12%
Silicates 1456 27.27%
Organic compounds 56 1.05%

Total 5340 100.00%
Marco E. Ciriotti

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Re: Statistical subdivision by crystal system and classes - 31 December 2017

Messaggio da Marco E. Ciriotti » mar 10 apr, 2018 15:41

Abbiamo visto nel primo messaggio che le valide specie minerali con sistema cristallino monoclino e ortorombico rappresentano più della metà del totale: 2903 su 5340 = 54.36%.

Ora questo 54.36% a quali classi appartiene?

Classes # %
Elements 26 0.90%
Sulfides and sulfosalts 369 12.71%
Halides 98 3.38%
Oxides 369 12.71%
Carbonates (+ nitrates) 148 5.10%
Borates 108 3.72%
Sulfates etc. 272 9.37%
Phoshates, arsenates, vanadates 601 20.70%
Silicates 875 30.14%
Organic compounds 37 1.27%

Total 2903 100%


Silicates + phosphates etc. = 1476 = 50.84%.
Marco E. Ciriotti

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