Copper sulphate around pipe through floor?

its probably sure to condensation on the pipes combined with some slight residue of acid or some such.

Copper will, if exposed to water and air long enough, turn green.

yup it's the condensation caused on the pipes due to the water in them being a different temp to the concrete they are in,

we have the hot and cold water pipes going into the concrete floor in the kitchen to go to the bog in our place, just had a plumber round to sort out the rats nest of plumbing behind where the cooker is going to go, and he told us that's why the pipes are greener where they enter the floor.

Possibly something to worry about: if the pipe is in contact with the concrete it may be corroding and could eventually fail. And if it's the mains feed that'll mean lots of water everywhere!

PS don't panic, but do make sure you know where your stopcock in the street is, and that it works (and that you've got a key for it if necessary - older ones are just like a tap handle that may be 3 feet down). And make sure others in the house know what to do, too.