My granite worktops

Hi

I have had black granite worktops in my kitchen for around 10 years. The seal between the worktops and the backsplashes & between worktops appears to be black/grey silicone (although I am not too sure?) I have added a picture. I think its perhaps a dark grey & its mat?
I have noticed it start to split in places and I really want to have a go at replacing it myself.

Can anyone with experience with sealants advise me what the 'sealant' is please?