Assertion: anthracite | /r/HasProperty | subjected to heat
Facets:
Source sentences:
text: Since anthracite coal had been subjected to the intense pressure and heat, it is the most compressed and hardest coal available.
text: Anthracite Coal is mined from the oldest geological formations, and therefore has spent the longest time underground and been subjected to the most pressure and heat, making it the most compressed and hardest coal.