Answer: -
Anthracite is the purest form of amorphous carbon
Explanation: -
Amorphous substances are those that do not have clear shape and opposite of crystalline. Coal is one of the amorphous forms of carbon.
Coal contains many impurities like sulphur, iron etc. Anthracite is a type of coal that has 92% to 95 %carbon and is the purest carbon containing variety of coal .
Anthracite is therefore the purest form of amorphous carbon