A type of coal called anthracite Is classified by geologists as a metamorphic rock and it is much harder than sedimentary coal so can you describe how you think anthracite forms?

Anthracite forms from bituminous coal through a process of metamorphism, where increased heat and pressure over millions of years cause chemical and physical changes. This transformation typically occurs deep within the Earth's crust, where tectonic forces elevate and compress sedimentary layers. As volatile compounds are driven off, the carbon content increases, resulting in the dense, hard structure characteristic of anthracite. This metamorphic process can be influenced by regional geological activity, such as mountain building or intrusions of magma.