Grey-brownish bone char are the best quality chars for absorption applications.
From the en.wikipedia.org
The quality of the bone char can be easily determined by its color.
From the en.wikipedia.org
Wood char is one possibility, but it has to have a coating for it to work as well as bone char.
From the sciencedaily.com
Bone char is also used as a black pigment.
From the en.wikipedia.org
Today it is considered a synonym for bone char.
From the en.wikipedia.org
Bone char is traditionally used in this role.
From the en.wikipedia.org
The process involved vacuum distillation of the crude material followed by filtration of the still residue through bone char.
From the en.wikipedia.org
It's a stonkingly good tranche of fish, roasted on the bone then finished over the grill to give a light char, and clearly comes from a large animal, which is as it should be.