Technical Information Needed for Preliminary Mine Planning
Assuming that the resource to be mined has been delineated with diamond-drill holes, the items listed in the following
paragraphs need to be established with respect to mine planning for the mineralized material. If this is an exploration project that has been drilled out by the company exploration team, the
following information should have been gathered during the exploration phase and turned over to the mine evaluation team or the mine development group. Such information includes--
• Property location and access.
• Description of surface features.
• Description of regional, local, and mineral deposit geology.
• Review of exploration activities.
• Tabulation of potential ore reserves and resources.
• Explanation of ore-reserve calculation method.
• Description of company's land position.
• Description of the company's water position.
• Ownership and royalty conditions.
• History of the property.
• Any special studies by exploration teams (metallurgical, geotechnical, etc.).
• Any social issues or environmental issues that have surfaced while exploration was being completed.
This isn't to say that more information on each of these subjects will not have to be gathered, but if it can be started during the exploration phase of the project, much time will be saved during the feasibility-evaluation and development phases.
Geologic and Mineralogic Information
General knowledge of similar rock types or structures in existing mining districts is always helpful. The first mine in a new district is far more likely to run the risk of making costly errors during development than are mines that may be developed later.
The geologic and mineralogic information needed includes the following:
to be mined within the overall area to be considered, including multiple areas, zones, or seams.
• The dip or plunge of each mineralized zone, area, or seam and the maximum depth to which the
mineralization is known.
• Continuities or discontinuities within each mineralized zone.
• Any swelling or narrowing of each mineralized zone.
• Sharpness between grades of mineralized zones within the material considered economically minable.
• Sharpness between the ore and waste cut-off, specifically--
-- Whether this cut-off can be determined by
observation or must be determined by assay or some special tool,
-- Whether this cut-off also serves as a natural parting, resulting in little or no dilution, or whether the break between ore and waste must be induced entirely by the mining method, and
-- Whether the mineralized zone beyond (above or below) the existing cut-off represents a current
submarginal economic value that may become economic at a later time.
• Distribution of various valuable minerals making up each of the potentially minable areas.
• Distribution of the various deleterious minerals that may be harmful in processing the valuable mineral.
• Interlocking of identified valuable minerals with other fine-grained minerals or waste material.
• Presence of alteration zones in both the mineralized and the waste zones.
• Tendency for the ore to oxidize once broken.
• Quantity and quality of ore reserves and resources with detailed cross sections showing mineral
distribution,
fault zones, or any other geologic structure related to the mineralization.
Structural Information (Physical and Chemical) The needed structural information includes--
• Depth of cover.
• Detailed description of cover, including type, structural features in relation to mineralized zone, structural features in relation to proposed mine development; and
information about any water, gas, or oil that might have been found.
• Quality and structure of the host rock (back, floor, hanging wall, footwall), including--
-- Type of rock.
-- Approximate strength or range of strengths. -- Any noted weakening structures.
-- Any noted zones of inherent high stress. -- Noted zones of alteration.
-- Porosity and permeability.
-- Presence of any swelling clay or shale interbedding. -- Rock quality designation (RQD) throughout the various zones in and around all the mineralized area to be mined out.
-- Rock mass classification of the host rock.
-- Temperature of the zones proposed for mining. -- Acid-generating nature of the host rock.
The structure of the mineralized material, including all of the factors in the above plus--
-- Tendency of the mineral to change character after being broken (e.g., oxidizing, degenerating to all fines, recompacting into a solid mass, becoming fluid, etc.). -- Silica content of the ore.
-- Fiber content of the ore.
Property Information
The needed property information includes--
• Details on land ownership and/or lease holdings, including royalties to be paid or collected according to mineral zones or areas.
• Availability of water and its ownership on or near the property.
• Details of surface ownership and surface structures that might be affected by surface subsidence.
• Location of the mining area in relation to any existing roads, railroads, navigable rivers, power, community infrastructure, and available commercial supplies.
• Local, regional, and national political situations observed with regard to the deposit.
Need for a Test Mine
From this long list of information, all of which is badly needed to do a proper job of mine planning, it is evident that data acquired during the exploration phase of the operation will not be
enough. Nor is it likely that all the needed data can all be
obtained accurately from the surface. If this is the first mine in a mining area or district, then what is probably needed during the middle phase of the mine feasibility study is development of a test mine. While this may be an expense that the ownership was hoping that it would not have to endure up-front, the reasons for a test mine are quite compelling.
From a mining point of view, a test mine will--
1. Verify expected ore continuity, thus eliminating disastrous surprises.
2. Allow rock strength to be assessed accurately, which will allow prudent planning and sizing of the commercial mine opening.
3. Allow mining efficiency and productivity to be
verified as it relates to drilling, blasting, and materials handling.
4. Permit more reliable studies of the nature of mine water inflows, which will allow for adequate water- handling equipment to be installed before problems are encountered.
requirements.
6. Confirm the character of the waste product and how waste will be handled in the commercial operation. From a metallurgical point of view--
1. Verify and optimize the metallurgical flow sheet with a pilot plant process that is continuous lock cycle
testing.
2. Determine size and type of equipment optimal for recovering the resource.
3. Determine type and amount of reagents that will lead to the best recoveries and concentrate grades. 4. Determine the required amount of water and how to achieve a water balance.
5. Predict concentrate grade, moisture content, and impurities more accurately.
6. Using bulk samples, assess the work index to a much better degree than with small samples. From an environmental perspective--
1. Demonstrate the ability to control the operation in such a manner that it will not do harm to the
environment.
2. Allow the project to study the waste characterization completely and determine any future problems.
3. If water discharge is involved, study the difficulty of settling the discharged water and determine what might be necessary to mitigate any future problems and determine if zero discharge is possible.
From the engineering design perspective--
1. Improve the ability to make more accurate cost estimates on the basis of better knowledge of the abrasivity of the rock and control of stopes and pit walls. This could actually lower the cost estimate since less contingency funds may have to be used.
2. Improve labor estimates so the productivity of each unit operation will be better understood.
3. Predict a more accurate schedule on the basis of unit productivities.
4. Lower the overall risk of the project in every aspect. From the perspective of expediting later mine development--
1. Explore early access to develop the commercial mine, thus shortening the overall schedule from the end of the feasibility study to the end of construction. 2. Consider how openings can be completely utilized as part of the commercial mine operation.
3. Because access to the underground opening will already exist, evaluate whether some shafts may be able to be raise-bored and then expanded by
mechanical excavation rather than by the more expensive conventional shaft sinking methods.
4. Consider a test mine as an ideal training facility prior to start-up of the commercial mine.