Karlis
Are you sure of the name?
I know of a black substance called EBONITE, a synthetic jet – Google tells us:

“Ebonite is a brand name for very hard rubber first obtained by Charles Goodyear by vulcanizing natural rubber for prolonged periods. For vulcanizing natural rubber he received patent number 3633 from the United States Patent Office on June 15, 1844.“

I learned to play the oboe for a while as a teenager- the sections of the instrument were made of Ebonite... And it was also used to make buttons and other small items...

Another simulant for jet is “Bois Durci”

Best wishes
Stefany