This is the nicest sink I’ve restored.  Before and after pics.  I made sure the whole thing was clean and then brought to 200+ grit then sealed with black silicone the with oil,  My own 100 year old refinished all brass drain too.  This is high-end Alberene stone. Yes, it’s the sink below in the blog under “Ooh what will this look like”?  covered in lead paint etc.  Thanks.  Eric, 508 826 9981.