Better coal should have following characteristics
(1) It should have high calorific value.
(2) It should have low moisture content.
(3) It should have low ash content
(4) It should have high calorific intensity. (Calorific intensity-maximum temperature attainable on complete combustion of coal with theoretical amount of air.)
(5) Size of coal should be uniform.
(6) Coking quality should be high (coal on heating gives a coke which is porous, hard, strong. And suitable for metallurgical needs, then the coal is known as caking coal)
(7) It should have very low content of sulphur and phosphorous.