I have another Woody Blackwell knife that is made of Imperial Jasper from Mexico. If you hold the knife up to the sun you can see through the outer edges of the stone. Its brilliant green.
The knife up in the front of this thread, made of Knife River flint has pieces of fern and other living material trapped inside the stone which you can clearly see- the knife is translucent when held up to a light source.
It is the sharpest thing I have ever touched to flesh, I can tell you that!