Ternary and higher gem-like compounds

Look out for rock forming minerals here

Alkali and earth alkali compounds tend to be rather soluble in binary compounds (you won't find many there) in ternary and higher compounds they tend to form less water soluble minerals.

• Ca(OH)₂ calcium hydroxide aka slaked lime (rather water soluble)
• CaCO₃ calcium carbonate (very slightly soluble)
• MgCO₃ magnesium carbonate aka magnesite (slightly soluble)
• Mg₃B₇O₁₃Cl boracite (very slightly water soluble)
• ... many more

In the earths mantle and crust silicon and oxygen are the most abundant elements. On the borther to earths outer core this changes to iron and nickle. Down there the most abundant minearls are made from mixture of those elements: olivine/peridot Of interest as diamondoid materials may be the pure end members of the mixing series:

• Fayalite Fe₂SiO₄
• Forsterite Mg₂SiO₄
• Tephroite Mn₂SiO₄ (less interesting since Mn is more scarce)
• Titanium Silicate TiSiO₄
• Titanite or Sphene CaTiSiO₅ (optical dispersion exceeding diamond; birefringent)

In nature when iron rich metal is available in stochiometric excess heterogenous pallasite is formed. This rock looks really beautiful and can be found in some meteroids.

Another interesting tertiary material would be CSiO ₄
a solid intermediate material between CO₂(gas) SiO₂(solid quartz): [1]