In our area of south central Pa. there are a lot of clay brick that were locally made for houses and even barns 150 to 200 years ago. The softer brick were not fired as hard and were used in the inside courses so I am told. I know from experience that they break and cut easily, and can be very soft compared to modern brick. They also can be very orange in color depending on the clay used. Old building salvage companies may have some, but scrounging around old demo sites, if accessible, should find some for free. I have also removed chimneys from old houses that were soft. Sawing as mentioned, would give a more consistantly fine powder. Also, wear a dust mask. If you know of any masory contractors who use a wet saw to cut brick on job sites, the sediment in the catch basin would work, but would be from modern hard brick, so I dont know if it will crush finer easily. I have not heard of this before as a stock stain pigment, would it be suitable for the violin red on Lehigh rifles? Roland