Demonstrated reserves — A collective term for the sum of coal in both measured and indicated resources and reserves. Deposit — Mineral deposit or ore deposit is used to designate a natural occurrence of a useful mineral, or an ore, in sufficient extent and degree of concentration to invite exploitation.
A. Abutment - In coal mining, (1) the weight of the rocks above a narrow roadway is transferred to the solid coal along the sides, which act as abutments of the arch of strata spanning the roadway; and (2) the weight of the rocks over a longwall face is transferred to the front abutment, that is, the solid coal ahead of the face and the back abutment, that is, the settled packs behind the face.
Molecular weights can be found in the NIOSH Pocket Guide to Chemical Hazards, chemical supplier lists, the NIST Chemistry WebBook or other online databases.. The numeric value of 24.45 in both formulae is the molar volume of air in litres at normal temperature and pressure (NTP), which is considered to be 25ºC and 1 atmosphere (101.325 kPa or 760 mm Hg or 760 torr).