Mining and civilization, stages of mining and feasibility study



Mining and civilization, stages of mining and feasibility study

Gideon Gipmai Yowa
(July, 2017)

Senior Instructor, Mining Eng. Dept., PNG University of Technology. PNG


1.    Civilization
Mining and agriculture have contributed to the early civilization of the human race and still remained the major primary industries today supporting the survival of humanity. Early civilization started when humans began to live a settled life by learning to cultivate, making simple implements such as pottery and tools, and herd animals.

Some 5000 years ago, more complex stages of civilization happened with development of towns, cities, language, writing, cultures and religion. The towns and cities became trading centers, specialization of jobs and social divisions evolved and a shift has occurred from Paleolithic Age to Neolithic Age.

The early civilization happened in Mesopotamia (Modern Iraq). Humans used the Euphrates and the Tigris Rivers for irrigation and herding. Archeologists have uncovered towns and cities buried under the earth along these rivers. There were some later civillisation along the Nile River in Egypt and Yellow River in China. 

For further reading of civilization, visit;
§http://www.pearsonhighered.com/assets/hip/us/hip_us_pearsonhighered/samplechapter/0205803504.pdf

§  http://www.essential-humanities.net/history-overview/stone-bronze-iron-ages/

§  http://www.theshorterword.com/stone-bronze-iron


2.    Mining history
The history of mining parallels with civillisation. Anthropologist designate the phases of civilization with respect to the dominant implements used at that period. The Stone Age (prior to 3000B.C.E) is the period where all the tools, weapons and implements were made from stone. The Bronze Age (3000 to 1000 B.C.E) is where copper and tin were smelted into bronze alloy for tools and weapons. The Iron (Steel) Age (1000 B.C.E to 1945) is where smelted iron with addition of carbon to create steel for tools and weapons.

Bronze is a superior alloy that human produce and has desired properties such as resisting corrosion, less brittle and stronger. However, its production cannot be sustained for long as the tin and copper do not exist together and may become depleted and scarce.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         

Iron is abundant in the earth’s crust and with the knowledge of smelting, iron and carbon produce steel that can be easily hammered into shape and can be re-sharpened if blunt as in the case of sword. The advantages of iron are its abundance that made it popular and that has replaced bronze.

The early records of pre-history mines were Flint mines in Europe. Flints (chert) were used for tools. Other know oldest mine is the Lion Cave in Swaziland for mining hematite.

For further reading of mining history, visit;
§  https://en.wikipedia.org/wiki/Mining

3.    Modern mineral demand
The Nuclear (Atomic) Age was from 1945 onward. After the end of WWII in 1945, the race was on for technology and space travel. Although the designation of time periods is not clear, after nuclear age, computer, information and space age all came into play around the same time till today.

The requirements of metals and materials diversify with the advance in science and technology. With the increase in human population, the demands for materials such as cars, computers, clothes, jewelry, houses, tools, and so on are increasing and the demand for metals increase proportionally. Although the metals prices fluctuate due to the global demands, the usage could be still higher.  As developing countries expand on infrastructure, the demand for metals will increase tenfold and recycling can be a plausible industry (NUEP, 2013).

For further reading on metals demand and outlook, visit;
§  http://www.unep.org/NEWSCENTRE/default.aspx?DocumentId=2713&ArticleId=9484

§  http://www.forbes.com/sites/greatspeculations/2014/10/20/for-metals-the-prevailing-demand-pricing-environment-and-future-outlook/

§  http://www.theguardian.com/environment/2013/apr/24/demand-metals-increase

§  http://www.riotinto.com/documents/Outlook_Full_Year_Results_2013.pdf

4.    Elements of mining
Understanding mining terminology is essential for beginners.

Mine-an excavation made on the crust of the earth to extract minerals for human consumption.
Mineral-a naturally occurring element or compound of fixed physical and chemical composition and structure.
Rock-any naturally formed aggregate of two or more minerals.
Ore-a mineral deposit of economic value and can be mined at a profit.
Gangue-valueless minerals within ore that is discarded as waste tailings.
Waste-materials outside the ore that are removed or developed through to access the ore.

Minerals can be further classified into fuels, metals and non-metals. Metallic ore are those of ferrous metals, the base metals, the precious metals, and the radioactive minerals. Nonmetallic ore are the diamonds and the industrial minerals. The mineral fuels are the hydrocarbons.

For further reading on essential concepts of mining, visit;
§  http://www.cienciaviva.pt/img/upload/Introduction%20to%20mining.pdf

§  Hartman. H (1987), Introductory Mining Engineering, John Wiley & Sons, pp2-4

5.    Stages of mining
The five stages of mining are: prospecting, exploration, development, exploitation and reclamation.

5.1      Prospecting stage
Prospecting is the hunt for mineral anomaly and several method and techniques are widely used;
§  Geological approach involves literature review, studying outcrop and sample stream sediment.
§  Geochemical approach involves analysing the chemical composition of the soil and the plants.
§  Geophysical approach involves airborne and ground survey. Rock properties are used including magnetism, resistivity, and density.

5.2      Exploration stage
The goal of exploration is to define and evaluate the tonnes, volume and grade of a mineral deposit. Several methods and techniques are widely used;
§  Geological logging of drillholes from diamond drilling programme
§  Excavation for bulk sampling for engineering and metallurgical test.
§  Assay for mineral concentration and grade.
§  Downhole survey of drillhole to confirm orientation and direction.

In the process of exploration, if the mineral deposit has a concentration of economic value, it is converted into a resource and the resource is converted into reserve for mining. 

An important process in the exploration stage is the feasibility study. Feasibility studies aim to address and evaluate all the areas related to mining and to decide whether the deposit is economically and safely viable to extract. Feasibility studies cover baseline environmental studies, geotechnical assessment, mineralogical studies, metallurgical processes, geology and spatial distribution of the deposit, mineral resource and reserve, conceptual mine designs and plans, workforce and labour requirements, equipment and infrastructures, market and economic analysis, political climate, social mapping, legal issues, regulatory compliance, and logistics.  

There are few levels of feasibility studies. A scoping study is undertaken normally during the exploration stage to consider any potential value to be added with further drilling. A preliminary feasibility (pre-feasibility) study is undertaken after several delineation of the mineral resource from additional drilling information and metallurgical test work. Pre-feasibility aims to establish viability of the project in terms of the economics, technicality and safety. Pre-feasibility and feasibility are similar in context except that feasibility may contain more accurate statement of resource and reserve that is bankable and can attract investors and financial institutions for financing the project. Furthermore a feasibility study contains a detailed execution and operational plan of the mine. 

An important decision for a mining engineer in feasibility study is the selection of the appropriate mining method. There are several factors that influence the selection including;

§  Geologic
-characteristics of the ore body (size, depth, shape)
-mineralogy and chemical composition
-structures and hydrogeology
§  Geotechnical properties
-rock strength and properties (SG, permeability, porosity)
-stress distribution and regime
§  Technology
-capital infrastructure and investment
-products and innovation making mining cost effective     (software, equipment
§  Environment effects
-health and safety, waste disposal, mining legislation
§  Economics
-Mine life, commodity price, cost of capital, cost of mining & processing

For further reading on feasibility study, visit;
§  http://www.enthalpy.com.au/wp-content/uploads/2014/06/EnthalpyCorporateProforma1100-The-Use-and-Abuse-of-Feasibility-Studies.pdf

§  https://www.ausimm.com.au/content/docs/branch/2013/melbourne_2013_02_presentation.pdf

5.3      Development stage
Development involves establishing access to the orebody, and also constructing the essential infrastructures (power, roads, airstrips, buildings, plants and so forth)

The capital (CAPEX) and the operational (OPEX) cost of an underground mine is more expensive than surface mine and the cost difference can range from two to five times more. 

Surface development requires fewer initial capital expenditures like dewatering system set ups, wall support and stability systems, haulage ramp, stripping and waste stockpiles. Other infrastructures like processing plants, magazines, workshops, buildings, equipment and machineries may vary slightly. However, those can be similar set ups for underground and cannot be treated as purely surface mine infrastructures.

Underground developments attract more capital expenses. The initial cost of decline or shaft can run into millions. For instance the waste stripping can cost around 10 to 20 dollar (US$) per tonne while the development cost of a lateral round can cost around 40 to 100 dollars (US$) per tonne (Porgera COG, 2013).

The high cost in development is attributed to the intensive ground support, high density of blasthole drill meters, high amount of explosives used, establishing of services like secondary fans, water and air reticulation, power cables and boxes. Other major or primary fixed infrastructures are the primary fans for ventilation, main pump stations for dewatering, substations for electricity, and paste reticulation for paste fill stopes, CAF plant for cemented aggregate filled stopes, compressor for air requirement of the drills, water reticulation and booster pumps, escape way and fresh air chambers, magazines, orepass system and chutes. The list of underground infrastructure outnumbers surface and this has contributed to the high start-up capital for underground mines.

5.4      Exploitation stage
Exploitation involves the extraction and processing of the ore to recover the mineral of interest using either surface or underground mining methods. The decision to use either method was discussed previously under feasibility study.

Economic viability plays an integral part in the decision making of the selection of either surface or underground methods of extraction. Other factors like safety, technology, statutory requirements, legal issues, and risk profile form part of the overall business plan.

Several mine design optimisation and comparison are done on the know reserve. Several cost analysis are done on the several design physicals and the one that yields the best and the highest return on the investment is the preferred design.

In most cases, a deposit that is closer to the surface (<100m) may attract the utilisation of surface methods while a deposit further deep may require an underground method. The cost involved in stripping the large volume of waste overburden to expose the orebody can make the entire project uneconomical then accessing the orebody through declines and shafts.

The processing facilities are set up for the beneficiation (crushing, grinding, concentration, smelting and refining) of ore. Each ore type and mineral requires slightly different set up of the processing plant. A set up of copper mine like Ok Tedi will be different to a gold mine like Lihir.

5.5      Reclamation stage
Reclamation stage involves restoring the natural environment to its former state or even better.

For further reading on mine closure and reclamation, visit;
§  http://www.miningfacts.org/environment/what-happens-to-mine-sites-after-a-mine-is-closed/

§  https://en.wikipedia.org/wiki/Mine_reclamation

6.    Key words
Following are the key words in this document.

Capital expense (CAPEX), exploitation, exploration, feasibility study, mine, mineral, operating expense (OPEX), processing, prospecting, reclamation, reserve, resource, surface mine, and underground mine.

Reference and further reading


Hartman. H (1987), Introductory Mining Engineering, John Wiley & Sons, pp1-12

Mining and civilization, stages of mining and feasibility study Mining and civilization, stages of mining and feasibility study Reviewed by Gideon Gipmai Yowa on July 13, 2017 Rating: 5

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