Help me please with cleaning Yorkshire stOne

[yorkshirebeautyspa]

I haven't posted on here got a loooong time ad I've been do busy over the last year! So long I've changed my account lol

Anyway back to business.... I have recently rented out another shop so I can open another salon, grabbed a bargain even though needed a lot of work. Removed smelly old carpet to find huge gorgeous Yorkshire stone flags :D only trouble is in my treatment room there was a red mark about 1x 0.5 meters which I think is where a carpet had previously been glued to the floor :(

Question is how can I clean this off? I have tried nitro mors and good old fashioned elbow grease but still red remains. Was going to try brick acid but was advised this may damage the lovely stone. Any more ideas mumsnetters?

Thanks x

[nextphase]

Caustic Soda?

Bleach? NOT AT THE SAME TIME

Good luck getting the stone clean. If no luck, could you put a rug on that bit, and leave the rest uncovered?