filler

Also contains definition of: grist
https://doi.org/10.1351/goldbook.F02363
Filler (also called grist) is a petroleum- or coal-based
coke
fraction of a green,
carbon mix
or formulation. Coarse particles, >0.425 mm, are sometimes referred to as tailings; fine particles, <0.074 mm, are referred to as flour.
Graphite
flour is also used as a filler.
Source:
PAC, 1995, 67, 473. (Recommended terminology for the description of carbon as a solid (IUPAC Recommendations 1995)) on page 489 [Terms] [Paper]