I made these puerh knives using wood that was found at our 80 year old house. There was a massive block sitting in our front yard for over a year until i finally picked it up and marveled at its weight. I was pleasantly surprised when I cut into it to find a ihad struck hard wood gold. 
The blade comes from hunting spear points that were likely used for smal game hunting.
I was surprised to hear they might be over 100 if not 200 years old but the scale of things is different over here!
It functions very well as a puerh knife and does well even with tough cakes.