Identifying magnesite flooring

TLDR: resistivity values and other identifying features for magensium oxychloride (Sorel) cement please.

I have a 1950s council house where the ground floor is 2 types (one room dark brown, one room red) of poured finish over a concrete slab. I want to put linoleum down, but the fitter is concerned we may have a magnesite (magnesium oxychloride cement) finish, which would cause issues with moisture.

Various sites (e.g. here and here) say you can identify magnesite by:

• holding a small piece in a gas flame – magnesite will "glow brightly"
• testing it using a 2-prong resistance-type moisture meter – magnesite will read full-scale even when dry (it’s conductive)

I’m pretty sure the dark brown is asphalt not magnesite as it melts and burns in a flame. The dark red finish does not. If you get it hot enough it glows red (as you’d expect), but that doesn’t seem very conclusive.

My question in 3 parts:

• how conductive is magnesite? What order of resistance would I see if I measured it with a multimeter?
• More detail on what "glows brightly" means (e.g. colour, how long does it glow for, does it brighten the flame or does the material itself glow)?
• Any other ways of identifying it?