What is the hardest and oldest type of coal called?

The hardest and oldest type of coal is called anthracite. It is formed from peat that has undergone significant geological pressure and heat over millions of years, resulting in a high carbon content and low moisture levels. Anthracite is known for its high energy content and is often used for heating and industrial purposes. It is characterized by its shiny, black appearance and is the most metamorphosed form of coal.