Can you make a fire extinguisher from chalk and sea shell mixture?

Answer 1

You can use any non-flammable material as a fire extinguisher, as long as it is in enough quantity and ground fine enough to exclude oxygen from the fire.
If you're talking about loading a chalk/seashell mixture into a pressurized fire extinguisher - I don't see why not, as long as the mixture is VERY finely ground, but you would be better off sticking with the powder that is made for them to avoid the possibility of clogging.

Answer 2

I don't think you'd have time