Stone wall repair – what mix?

I’ve got a stone garden wall and some of the stones at the top (capping stones?) are loose and need reattaching.
The thick slate hearth for the wood burner has also come loose.
Any advice on what I should use to do the job? I’ve got sharp sand and can easily get hold of cement.
Thanks in advance …

4:1

Isnt that a Lime Mortar job? (For the garden wall)

Something I saw suggested yes it is lime mortar, and so I did a bit more reading and got quite scared. Any tips??

I use 2:5, lime to sharp, for the wall.
Cement is too hard for sandstone.

Cement is too hard for sandstone.

And most sedimentary rocks, see the Beauchamp Tower at the Tower of London for the mess OPC pointing can make of ragstone.

What COLP says.

Forgot to say, don’t do the wall if the overnight temps are forecast to drop to near freezing with 3 or 4 days of the work. The mortar could suffer frost damage.