How to tell what is lime mortar or concrete pointing?

[Woodpecker2]

We hope to repoint the whole front of the house at some point - due to damp, but also it looking quite untidy. But I’m not sure how much of what there currently is lime, if any? And whether to patch up any gaps or dig out particularly dodgy bits in the meantime. Seems to be a patch work or something lighter and then something darker - but I am really not sure (as a total novice) what is what!
Tried to upload more photos but apparently they’re too large

 

[housegolem]

If its grey it is most likely cement based, whiter is generally lime.

Hardness is also a good indicator, if it's lime it should be softer.

I've raked out nearly my entire house for repointing with an old flat head screwdriver, where lime is present!! Bad cement repairs are tougher but can often be chipped off if there not too deep. If not you might have to resort to the angle grinder and diamond disc on deeper repairs.

 

[Stevers]

The dark mortar looks to have a brushed finish which is typical of modern work and looks recent. The white flecks showing in it could well be from hydrated lime that's been around a bit too long. That would suggest the darker mortar is a cement/lime mix. By comparison the lighter mortar is more typical of older work, and is very likely to be lime.

 

[LadyArowana]

There’s an old thread on this topic which might help https://www.periodproperty.co.uk/forum/threads/is-it-lime-or-cement.15532/

 

[Woodpecker2]

Thanks all, very helpful!

 

[Woodpecker2]

I’ll try the fizz test!