This is a small jar of anthracite coal, nut sort, from Pennsylvania.
There is approximately 0.55 to 0.66 pound (250 to 300 grams) of coal inside the jar. There will be some slight variation from jar to jar.
Anthracite coal, or hard coal, has the highest carbon content, the greatest hardness, and the fewest impurities.
This is "nut coal". Nut is a measurement of size, not content. The standard sizing of nut coal is 13/16 to 1 9/16 inches (20.62 to 39.70 millimeters). Some random pieces measured 1 to 2.75 inches.