Difference between revisions of "Salts of oxoacids"

Revision as of 11:00, 26 June 2021

The X-O-X bonds present in those compounds increase the space between the spacially linking X atoms. This lead to a lower density of bonds in cross sections inclusion of bigger voids thus higher porousity. Due to the porousness of these compounds it is harder to get the surfaces flat - figuratively like the surface of a pumice stone. It's impossible to get them as smooth as passivated diamond. [todo: investigate wheter superlubricating bearings can be constructed from these types of diamondoid compounds]

(wikipedia:oxoacid)

Silicates (& Quartz)

Silicates typically have pretty good mechanical properties.
Typically Mohs 5-6 sometimes up to almost ~8.

Of interest as base materials may be the pure end members of the mixing series of olivine (wikipedia) / peridot (wikipedia)
From Mg₂SiO₄ forsterite to Fe₂SiO₄ fayalite.
And especially the associated high pressure modifications.
High pressure modifications tend to have higher crystal symmetries and mechanical strength at the cots of a bit of thermal stability.

Olivin/Peridot end-members and their low pressure stable stable high pressure modifications

Low pressure magnesium endmember forsterite:

• Mg₂SiO₄ Forsterite – orthorhombic dipyramidal – Mohs 7

High pressure modifications of fortserite:

• Mg₂SiO₄ wadseylite (wikipedia) – sorosilicate – ortorhombic – dipyramidal – Mohs ?? – mid pressure crystal structure
• Mg₂SiO₄ ringwoodite (wikipedia) – nesosilicate – cubic – Mohs ?? – 3.9g/ccm – high pressure crystal structure – 3D structure (de)

Low pressure iron endmember fayalite:

• Fe₂SiO₄ Fayalite – orthorhombic dipyramidal – Mohs 6.5-7.0 – 4.39g/ccm – 3D structure (de)

High pressure modifications of fayalite:

• γ-Fe₂SiO₄ ahrensite – cubic – 4.85g/ccm – high pressure crystal structure of fayalite – 3D structure (de)

Neo-polymorphic transitions

The low pressure modifications forsterite and fayalite are isostructural (atoms at the same places).
This allows for neo-polymorphs spanning the natural mixing series. Just checkerpatterned as deisred.
(wiki-TODO: Magnesium and iron are pretty far apart in the periodic table – find out why they behave so similar electronically in these minerals)

Q: Is there an iron analog to wadseylite?

Ringwoodite (Mg) and ahrensite (Fe), while both cubic, have quite different structure. No neo-polymorphs here.
But Maybe unnatural iron-ringwoodite and magnesium-ahrensite can be piezosynthesized.
At least a little bit of substitution should work if electronic similarity still holds in these high pressure modifications

Silicates of further rather common elements

Calcium:

• γ-Ca₂SiO₄ Calcio-Olivine – Mohs 4.5 – orthorhombic
• β-Ca₂SiO₄ Larnite – Mohs 6 – monoclinic (?)

• Ni₂SiO₄ Liebenbergite (de) – (Mohs 6-6.5 or 4.5?) -- orthorhombic
• Mn₂SiO₄ Tephroite (maybe less interesting since Mn is more scarce) – orthorhombic dipyramidal – Mohs 6
• TiSiO₄ Titanium Silicate (no natural mineral here?) [1] (broken)

Beyond that adding one more element there are an innumerable amount of natural silicates around.

Some semi random picks of other silicates

Misc, Not exactly a salt but related ...

• PbCa₃Zn₄(SiO₄)₄ esperite [2] Mohs 5-5.5 (unabundant zinc | exceptionally hard lead mineral) Specific gravity: 4.28-4.42

Other pages listing silicates of interest

Context specific silicates are also listed on these pages:

• Ternary and higher gem-like compounds
• s-block metals – lists some alkali and earth alkali silicates (among other compounds)
• Iron – lists a few iron silicates

Phosphate minerals

(wikipedia)

• Especially interesting: Hydoxy- Fluor- & Clorapatite Ca₅(PO₄)₃(F,Cl,OH) - (Mohs 5 defining mineral) - a biomineral [3]
• Lazulite (wikipedia) & Scorzalite (wikipedia) magnesium iron aluminium phosphates - (Mohs 5.5-6)
• Phosphophyllite (wikipedia) - zinc iron phosphate - rather soft (Mohs 3.5)
• Pb₅(PO₄)₃Cl pyromorphite (wikipedia) - relatively hard for a lead mineral (Mohs 3.5)
• Y(PO₄) Xenotime (wikipedia) - rare yttrium - high symmetry (tetragonal) - (Mohs 4.5)
• Al₂(PO₄)(OH)₃ augelite [4] Mohs 4-4.5
• FePO₄ heterosite Wikipedia:Heterosit(de) Mohs 4-4.5
• MnPO₄ purpurite [5] Mohs 4-5 (unabundant manganese)
• (MgFe)2PO4F magnesium and iron wagnerite [6] Mohs (?)
• FeAl2(PO₄)₂ anhydous iron scorzalite [7] Mohs 6
• MgAl2(PO₄)₂ anhydous magnesium scorzalite Mohs 6
• Zn₂Fe(PO₄)₂•4H₂O phosphophyllite [8] Mohs 3.5 (soft)

Carbonate minerals

(wikipedia - minerals) (wikipedia - artificial)

• Calcite Mohs 3 (defining mineral) & Aragonite Mohs 3.5-4 - calcium
• Magnesite Mohs 3.5-4.5 - magnesium
• CaMg(CO₃)₂ Dolomite [9] – Mohs 3.5-4 – Trigonal Rhombohedral
• Siderite - iron
• Smithsonite - zinc
• Malachite & Azurite - copper
• Rhodochrosite - manganese (rare)
• ...
• Mg₃Ca(CO₃)₄ Huntite [10] Mohs 1-2 (very soft!)
• PbCO₃ Cerussite [11] Mohs 3-3.5 (soft)

Sulfate minerals

(wikipedia)

Sulfate minerals are generally rather soft with few exceptions.
One of the harder ones is brochantite (wikipedia) - (Mohs 3.5-4)

• CaSO₄ anhydrite [12] (decomposes slowly to hydroxyde gypsum)

Borate minerals

(wikipedia)

• Mg₃B₇O₁₃Cl Boracite (wikipedia) - (Mohs 7-7.5)
• Mn₃B₇O₁₃Cl Chambersite (wikipedia) - (Mohs 7)

• Al₆B₅O₁₅(F,OH)₃ Jeremejevite (wikipedia) - (Mohs 6.5-7.5)
• Mg₇(BO₃)₃(OH)₄Cl Karlite (wikipedia) - (Mohs 5½)
• Ca₂B₅SiO₉(OH)₅ Howlite (wikipedia) - soft (Mohs 3.5)
• MnSn(BO₃)₂ Tusionite (wikipedia) - (Mohs 5-6) - tin
• CaZrAl₉O₁₅(BO₃) Painite (wikipedia) - rare zirconium (Mohs 8)
• ...

Nitrate and Aluminates

All rather water soluble. See: (wikipedia - minerals) (wikipedia - artificial)

Aluminates: (wikipedia)

Salts of metal oxoacids

TODO ...

Related

• Oxygen

External links

Wikipedia:

• Solubility chart: https://en.wikipedia.org/wiki/Solubility_chart
• Oxoacid
• Category:Oxoacids