fu·sain 
(fyzān, fy-zān)
(fyzān, fy-zān)n.
1.
a. Fine charcoal in stick form, made from the wood of the spindle tree.
b. A sketch or drawing made with this charcoal.
2. A black, friable band in bituminous coal, characterized by a fibrous structure and silky luster.
[French, spindle tree, charcoal made from its wood, from Vulgar Latin *fūsāgō, *fūsāgin-, spindle (formerly made from the wood of a spindle tree), from Latin fūsus.]