Mortar has fine rock called, "Sand" in it. There is also finely pulverized limestone in it that helps harden it.
30 minutes to the touch and 24 hours to be functional. If the Mortar is being used in a fireplace or chimney a week or more may be required.
the flame ops us a wtare to make it harden
A reduction in temperature.
leaving it out in the cold or puting it in a freezer
If you mix cement ,sand and water you get mortar If you mix cement and stone pebbles or chips you get concrete Concrete.Sometimes gravel is mixed with it, too.
Minerals like calcium and phosphorus :)
They contain a substance called hardener.
Keratin... it's a natural substance that makes the nail harden.
Volcanic activity in which lava and magma cool and harden into rock and stone.
rennin is an enzyme which makes milk harden in your stomach so that it can be broken down and digested
lava, because it forms outside of Earth's surface and makes rocks that harden