support for expressing solid solution in formula definitions

[jonnyprouty]

Is there a way to express solid solution using chemical formula? By solid solution, I am referring to formula describing a crystal composed of different kinds of atoms occupying equivalent sites within the crystal lattice. This is a common occurrence for natural materials, i.e. minerals. I've included a few examples below:

olivine
Commonly expressed as (Mg, Fe)₂SiO₄, equivalent to (Mg_1−xFe_x)₂SiO₄. The first formulation is a very common method used by geochemists to denote solid solution where in this case Fe and Mg exist and can vary in nature from pure Mg to pure Fe, with any ratio of the two possible.

hornblende
This family of minerals is particularly complex, with numerous varieties existing, a product of numerous solid solution series existing:

• Magnesiohornblende-ferrohornblende, Ca₂[(Mg,Fe)₄Al]Si₇AlO₂₂(OH)₂
  • (Mg,Fe)₄ equivalent to (Mg_1-x,Fe_x)₄
• Tschermakite-ferrotschermakite, Ca₂[(Mg,Fe)₃Al₂]Si₆Al₂O₂₂(OH)₂
  • (Mg,Fe)₃ equivalent to (Mg_1-x,Fe_x)₃
• Edenite-ferroedenite, NaCa₂(Mg,Fe)₅Si₇AlO₂₂(OH)₂
  • (Mg,Fe)₅ equivalent to (Mg_1-x,Fe_x)₅
• Pargasite-ferropargasite, NaCa₂[(Mg,Fe)₄Al]Si₆Al₂O₂₂(OH)₂
  • (Mg,Fe)₄ equivalent to (Mg_1-x,Fe_x)₄
• Magnesiohastingstite-hastingsite, NaCa₂[(Mg,Fe)₄Fe3+]Si₆Al₂O₂₂(OH)₂
  • (Mg,Fe)₄ equivalent to (Mg_1-x,Fe_x)₄

Any thoughts as to feasibility of expressing such non-stoichiometric formulae? Thanks in advance!

I should note I borrowed heavily from wikipedia for the examples. Thanks Wikipedia editors!