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VII-5
DEFINITIONS OF ORE RESERVES VERSUS ORE RESOURCES
The mining industry and the U.S. Bureau of Mines (USBM) maintain a rather
restricted interpretation of what can be called reserves. In short, this means that the ore
in-place can be mined under current economics and technology. Others, particularly the
USGS, will use the term resource to defme in-place mineral-bearing bodies that have the
potential to be mined, which is a more liberal interpretation. A full discussion of these
two terms can be found in USGS-USBM (1980).
The in-place potash-bearing 4th and 10th ore zones that were quantified meet the
more restrictive definition of reserve because they would provide reasonable profits at
current market values for potash products, and can be extracted with currently available
mining and processing methods. In addition, most of the 4th and 10th ore zones would be
classified as ore reserves by order of the Secretary of the Interior dated October 21,
1986, according to which four feet of 10 percent Kp as sylvite or four feet of4 percent
Kp as langbeinite or equivalent combination ofthe two minerals defmes potash reserves.
The term Lease Grade Reserves was used to defme those resources that meet or exceed
the above criterion and thereby become reserves.
On the other hand, the reserves quantified for the 2nd, 3rd, 5th, 8th, 9th, and
11th ore zones should be considered resources. The resources may become minable if
new thin-seam mechanical miners are developed. Solution mining might be applied to
those that are sylvite-bearing, but not to those containing the relatively insoluble langbeinite.
To be classified as an ore reserve also means that the geometry of the in-place ore
is well defmed by either reliable drilling or actual sampled exposures, whether it be from
outeroppings or mine faces underground. In case of WIPP the reserves must be regarded
as drill-defmed only.
The spacing of drill holes within the WlPP boundary is apprOximately on one-tnile
centers. This meets the current BLM requirements to defme ore reserves, which allows a
projection of three-quarters of a mile outward from an existing hole (or 1.S mile spacing).
However, it is common for some of the I;lC3lby tnining companieno close up the
drill spacing to 2000 or even lOOD-it spacing to define better ore-bearing areas in advance
of developing detailed mining plans. Nonetheless, the potash industry probably would
agree that the spacing within the WIPP boundary meets their criteria for defining ore
reserves, and certainly is adequate to defme their life-of-tnine reserves.
Outside of the WIPP boundary a clear-cut line cannot be drawn between what is
to be classed as ore reserve or ore resource, because the drilling information is incomplete,
partiCUlarly to the west, and the of lack any subsurface information whatsoever on
the immediate southern and eastern boundaries of the WIPP Site. More discussion of the
validity of the estimates of reserves and resources adjacent to the WIPP Site accompanies
the following descriptions of individual ore zones.
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