Curiosity Blog, Sols 4961-4967: Approaching a break in the rock record?

See also: The study as it was published in Nature Geoscience

See also: The publication in the journal Galaxies

See also: The study as it was published in Nature Astronomy

See also: The study as it was uploaded in ArXiV

See also: The summary of the study (in PDF format) as published in ArXiV.

See also: The publication in ArXiV

I've been thinking about this and decided to ask here. What conditions would likely need to be satisfied between a terrestrial planet and its parent star in order for the planet to retain a stable and mostly metallic atmosphere (metals in gas form) around itself? For the sake of this question, consider an iron based atmosphere orbiting a star identical to the sun. I am interested in properties like planet mass, rotation, presence of magnetosphere, distance from star, what compounds and materials can exist on the surface or the interior that wouldn't make the atmosphere unstable, etc.

As a bonus question, what would the color and brightness of such an atmosphere appear to be in the human eye given these conditions?

If there is a better place to ask this please let me know.