There are just a few areas in Saltaire that have been left with the authentic stone cobbles (properly known as setts... I think because they are flat brick shapes rather than rounded stones). You can see them on my photo of Albert Terrace and in a small section at the bottom of Victoria Road. Salts Mill yard is also paved with setts. I had assumed these to be original and unchanged since Victorian times. But I have recently read a wonderful book called "Salt and Silver" by Jim Greenhalf, which is the story of Salts Mill and the two visionary men - Sir Titus Salt and Jonathan Silver - with whom its history is entwined. There is a photograph in the book, taken in 1988, of Jonathan Silver looking at the setts being relaid in front of the mill. So it seems that, after he bought the near-derelict Mill, he arranged for the tarmac to be ripped up and the setts restored. I like him even more now!
There is an amusing tale in the book that Jonathan, always an enthusiast and very 'hands on' throughout the restoration of the Mill, was one day attacking the tarmac with gusto with a pneumatic drill, to the evident surprise of the branch director of Barclays Bank (who loaned money to finance the project) who chose that moment to arrive with an entourage of officials!