Was it a Xiaguan brick?
Also, get another pick, an icepick, the tuocha pick might not have been built well enough. It is dangerous to use knives of any sort. People have stabbed themselves trying that.
Set the brick on one of the edges in your tray, grip the icepick with your use-hand. With that same use-hand, use the bottom of the palm to rest on top of the brick, firmly, with whatever grip you can manage (most likely you will only manage to rest the edge of the palm on the brick rather than any sort of grip). From that tip of the pick's slight angle above the edge of the brick, lower it using your wrist. This seems to maximize leverage for those incredibly dense bricks, and you have the option of non-use hand to grip the top of the pick as well, and add another bit of arm strength.
Well, that's how I did it for those 100g XZH Zhangjiawan bricks, which were the densest I've ever had to deal with.