I love using Triangle bricks. I do masonry part time, on the side etc. and when I'm engaged in the work, I prefer Triangle's products ability to cut, trim, etc. easily, quickly and accurately. When I'm pushing a 14-15 hr shift, 800+ king size bricks, working against multiple string lines, mixing my own mortar etc. I don't want to fight cutting/trimming brick, I want the brick to cut (chisel or saw) right the first time...and this is why I prefer Triangle. They are simply more fun to work with than most of their competitors, at least the ones I've used. Oh yeah, cool video, thanks for sharing the "behind the scenes" of brick making!
Shale is just consolidated clay. Processing shale for making bricks is merely a case of 'unconsolidating' it. Durability is a function of clay chemistry, firing time, and firing temperature - how mature or vitrified it becomes. However, too vitrified and the mortar won't stick to it. But that's not a problem if you're making pavers.