A very high quality, opaque, cool, black.
I think Rublev's description says it all;
"Bone Black is fine grained with good tinting strength. Bone black, also known as ‘bone char’ or ‘animal charcoal’, is produced by charring animal bones. The bones are heated to high temperatures without oxygen. It consists mainly of calcium phosphate and a smaller amount of carbon. Ivory black is an artists’ pigment formerly made by grinding charred ivory. Ivory is no longer used because of the expense, and because animals that are natural sources of ivory are subject to international control as endangered species. Today, ivory black is considered a synonym for bone black. Among artist pigments, ivory black is considered a better grade of bone black, consisting of 15 percent or more of carbon. We use only the best grade of bone char containing at least 18 percent carbon. Rublev Colours bone char oil paint is named ‘Bone Black’ because we use the name of the actual pigment for our colors"
Binder: Linseed Oil
Tinting Strength: High
Drying rate: Medium