S-block metals

s-block metals as material filler

The lighter ones of the alkali- and alkaline earth metals (the non-noble metals in the left s-block of the periodic table) belong to the most abundant elements around. Thus its an iteresting question wheter those elements can be combined with other abundant ones to make structural building materials.

solubility issue

The s-block metals need to be combined with other elements not only because metals are not very suitable for mechanosynthesis but also because they are extremely reactive in pure form. A self passivation oxide layer film like the one that macroscopic blocks of magnesium have is obviously not possible on nano sized building blocks. In contact to air oxidation would go down right to the core of the building block and blow up the part twice in volume destroying it completely.

Since s-block metals are so electropositive they tend to toss away their shell electron or pair of shell electrons and thus tend to form ionic salts. Such a salt usually has the form:

• positively charged s-block-metal + negatively charged nonmetal-acid

Polar salts of this form are easily dissolved in water since water is a polar solvent. But good water solubility is not what one usually wants from a typical building material - especially not if the solvent is toxic like it is the case with many beryllium compounds. So the focus here will be on the few non or barely water soluble compounds.

barely soluble salts (*ates)

harder compounds (silicates only?)

Some harder silicate compounds containing aluminum too are:

• LiAl(SiO₃)₂ spodumene Mohs 6.5-7 (contains unabundant lithium)
• KAl(SiO₃)₂ leucite Mohs 5.5-6
• NaAl(SiO₃)₂ jadeite (a chain/band silicate) Mohs 6.5-7

---

• NH₄[AlSi₃O₈] buddingtonite Mohs 5.5 (insoluble ammonium compound!)
• Li[AlSi₃O₈] (unknown? - in literature - are there crystals?)
• K[AlSi₃O₈] orthoclase (feldspar member) Mohs 6 (defining mineral) and amazonite Mohs 6-6.5 and sanidine (endmember?) Mohs 6 and microline Mohs 6-6.5
• Na[AlSi₃O₈] albite (sodium placgioclase feldspar) Mohs 6-6.5

---

• LiAlSi₄O₁₀ petalite Mohs 6-6.5
• KAlSi₄O₁₀ (unknown? potassium petalite)
• NaAlSi₄O₁₀ sodium petalite

---

• CaAl₂Si₂O₈ anorthite (calcium plagioclase feldspar) Mohs 6
• MgAl₂Si₂O₈ magnesium aluminosilicate (there are various associated hydroxide minerals => solubility?)
• Fe or Cr replacing Al => unknown

Garnets containing aluminum:

• Ca₃Al₂(SiO₄)₃ grossularite Mohs 7-7.5 (an ugrandite garnet and nesosilicate)
• Mg₃Al₂(SiO₄)₃ pyrope Mohs 7-7.5 (a pyralspite garnet and nesosilicate)

Ugrandite garnets are defined by their calcium content:

• Ca₃Al₂(SiO₄)₃ grossularite Mohs 7-7.5
• Ca₃Fe₂(SiO₄)₃ andardite Mohs 6.5-7
• Ca₃Cr₂(SiO₄)₃ uvarovite Mohs 6.5-7 (contains unabundant chromium)

Magnesium analogs to ugrandite garnets:

• Mg₃Al₂(SiO₄)₃ pyrope Mohs 7-7.5
• Mg₃Fe₂(SiO₄)₃ (unknown?)
• Mg₃Cr₂(SiO₄)₃ Knorringite Mohs 6-7

softer compounds

When systematically building combinations of s-block metals and d-block nonmetal acids one can find some barely soluble compounds:

• calcium carbonate CaCO3 (limestone/chalk ... calcite/aragonite/vaterite)
• calcium phosphates (similar to hydroxyapatit bone tooth-enamel)
• calcium silicate CaSiO3 (dry wall plates ... wollastonite)
• magnesium silicate Mg2SiO4 (forsterite - no crystal water - pretty hard - neosilicate - earth mantle mineral)
• magnesium silicate Mg3Si4O10(OH)2 (talc - a hydroxide - way too soft for a building material)

Beryllium silicates:

• beryl Be3Al2(SiO3)6 (cyclosilicate) wikipedia
  varieties: emerald (green Cr), aquamarine (blue Fe), red beryl (red Mn), goshenite (colorless), heliodor (yellow Fe), and morganite (pink Mn)
• phenakite Be2SiO4 (neosilicate)
• bertrandite Be4Si2O7(OH)2 (hydorxide - pretty hard - sorosilicate)

non salts but (*ides)

Probably the simplest barely soluble earth alkali compounds (that are not salts) are:

• MgO (periclase ... magnesia) magnesium oxide (nontoxic)
• CaF2 (fluorite) calcium fluoride
• BeO (brommelite Mohs 9) beryllium oxide
• BeAl2O4 chrysoberyl

[todo:]

• [find some insoluble alkali compounds Li Na K]
• [maybe find some compounds of the heavier and less abundant ones (Rb & Cs) (Sr & Ba)]
• [treat aluminum as special case]