How do I remove scratches from bluestone steps?
My apologies to Fresh Codemonger, mineral oil will darken the steps and will leach back out over time showing the scratches from clearing the snow.
Use Muriatic acid to etch a new surface. I have had some success in removing most of the scratches in other slabs.
You will need to dilute it, apply it with a stiff bristle brush, use gloves and eye protection. It can be bad stuff, if handled improperly. Depending on the strength of the acid, I dilute 1 cup with about 2 gallons of water. I only suggest this as an example for dilution.  As a caution, too strong of solution will yellow the stone or anything it gets on, besides burn real bad if it gets on your skin.
It will also need to be rinsed thoroughly.
Here is a online document for etching concrete, which is the same process as etching stone, just that there is not painting going on afterward.
Another way to do it by &quot;flaming&quot; the surface with an acetylene torch after wetting the surface. This is the way the edges were finished on our treads after a saw cut the slabs to size. I am certain the top surface was flamed as well since your tread surfaces are not natural cleft.
If you do choose to do it this way you will need a face shield since the steam created by the flaming sends burning hot flakes of stone popping in the air at high speeds.
Here is a video on it here
The masonry cement will need to be protected from the extreme heat of the torch, it will cause the mortar in the risers to really blow out. that would NOT be good