Do you own the mineral rights? In Kentucky, ownership of property may be separated into surface rights, timber rights, mineral rights, etc. If you do not own coal mineral rights, then you do not own the coal on your property. On the other hand, you may have mineral rights to coal on someone else's property. You should know the type of ownership you have before you proceed any further.
Where is your property? Next, you must determine whether or not your property is within one of the two coal fields. If your property is not situated on coal-bearing rocks, you are not going to have coal on your property. Examine the Geologic Map of Kentucky to see if your county is in one of the coal fields. If your county is on the border of a coal field, you may have to examine a more detailed map to see if your property is on coal-bearing rocks (i.e., Pennsylvanian rocks). To do this, you will have to locate your property on a topographic map. Having done this, examine your property on a geologic quadrangle map. The geologic quadrangle maps (also called "GQ's") are the same scale as the topographic maps. The geologic map will indicate whether your property is on Pennsylvanian rocks or not.
What coal beds do you have on your property? The geologic quadrangles will give some indication about the coal beds that outcrop on your property, although all of them will not be mapped. Deep coal beds will not be indicated on the geologic quadrangle maps. Available boreholes may provide additional information.
Calculate coal reserves for each coal bed: This is the complicated part; most people would hire a registered consulting geologist or registered mining engineer for this. The process is explained here, in simplified terms. Each step is done separately for each of the coal beds under consideration. The first step is to gather as much coal thickness information as possible for the target coal bed. Information may be obtained from the Kentucky Geological Survey Coal Thickness Data Base, KGS Borehole Data Base, files of local coal companies, and neighbors and by examining outcrops, digging out the coal, and possibly drilling boreholes (drilling can be paid for by interested companies). After coal thickness data are gathered, a map showing coal thickness trends (isopach map) is constructed for the target bed. Property lines and the target coal-bed outcrop lines are added to the map. Next, the area for each thickness class must be measured (generally in acres). This process is called planimetry. Planimetry measures the area of the property. With the area and thickness known, a volume of coal can be calculated, and from this volume, a total tonnage can be derived. Planimetry can be done by hand using several methods, but the most accurate is with a mechanical device called a planimeter. Planimetry can also be done accurately by a computer using special software. From the calculated areas and the projected thickness trends, a gross reserve estimate can be calculated.
The gross reserve estimate is a volume calculation based on a conversion factor for bituminous coal, of 1,800 tons for every acre for every foot of coal. To estimate the tons of bituminous coal on a property, the formula is:
Acres * Coal thickness* 1,800 tons/acre-foot = Tons of coal on your property
Acres = the number of acres underlain by a coal bed
Coal thickness = the average coal thickness in decimal feet for that area underlain by coal
If you have 4 acres of property underlain by a coal bed, and the coal bed thickness is 5.2 ft. then,
4 * 5.2 * 1,800=37,440 tons of coal
More about this calculation: How it is derived from coal density (specific gravity) and area
Many other factors must also be examined to determine what the coal is worth:
quality, mineability, transportation, available market, etc.