Doug--

While the exact composition may be proprietary with BM, from what I've seen at manufacturing trade shows, the "stones" for "stonewashed" are a ceramic medium somewhat akin to ceramic knife sharpeners.

An engineer friend of mine took me to several trade shows with him, because of my interest in tools & gadgets (go figger!). The polishing devices I saw could only be described as vibratory polishers on steroids! If any of you are reloaders & are familiar with the small vibratory polishers sold by Dillon & others, simply imagine the same thing, but with a bin from 4 to 6 ft in diameter.

The triangular ceramic media I saw demonstrated was used to debur parts, and imparted a stonewashed finish. Size, compostion, & shape of media were variables that could be altered to give desired results.

Just my $0.02.

David