[maccha]

My chem textbook says that magnesium requires heating to react with oxygen. It then says though, that it does not react with water because of a naturally occurring magnesium oxide coating.. how can this coating be naturally occurring if magnesium must be heated to react with oxygen?

[aurophilic]

That is confusing. Although it will form a small coating on the surface of a piece of metal, I think they must mean two different things here.

When they say react, I think they mean, what does it take to get magnesium to ignite in a vigerous oxidation reaction that will burn under water or in a block of dry ice, and in the case of ther thin film they mean a very minimal reaction.