NAME: AZEEZ RASAQ ADEBAYO

DEPT: EARTH SCIENCES (GEOLOGY OPTION)

MATRIC NO: 100406020

COURSE CODE: GEY415

COURSE TITTLE: MINING GEOLOGY

1.On an outlined map of Nigeria, show the variousminerals resources distribution in Nigeria

ANSWERS

Figure1. The Map Showing the Location of variousMineral Places in Nigeria.

LEGENDS:

2.Discuss the appropriate mining process ortechniques that can be adopted for a Gold mine

ANSWERS

ROMAN MINING METHOD:The gold occurred here is shown by the discovery of ahoard of gold ornaments in the 18th century. Objectsfound included a wheel brooch and snake bracelets, sonamed because they were soft enough to be coiled aroundthe arm for display. All the objects are now held inthe British Museum, and displayed in the Romano-Britishgallery. A sample of gold ore was found at the site byHenry de la Beche in 1844, confirming the presence ofgold.

Occurrence: Gold usually occurs in its metallic state,commonly associated with sulphide minerals such aspyrite, but it does not form a separate sulphidemineral itself. The only economically importantoccurrence of gold in chemical combination is withtellurium as telluride minerals.

Most gold mined in Australia today cannot be seen inthe rock. It is very fine grained and mostly has aconcentration of less than 5 grams in every tonne ofrock mined. Primary gold deposits are formed from gold-bearing fluids at sites where the chemistry andphysical characteristics permit gold deposition.Primary deposits are often modified by weathering, butsecondary deposits are formed only after the completebreakdown of the host rock has occurred. Liberated goldis concentrated in alluvial (placer) deposits.

Hydraulic mining

Figure2a.The aqueducts at Dolaucothi Figure2b.Map ofthe gold mine

The water was stored in the tanks and then releasedsuddenly, the wave of water sweeping away the soil toreveal the bedrock and any gold-bearing veins beneath.Pliny the Elder gives dramatic account in his NaturalisHistoria of the method, possibly derived from hisexperiences in Spain. The method is known as hushingand survived in use until the 19th century in Britain,and into the 20th century in the goldfields of Africa.A not dissimilar method is used today in exploitingalluvial tin deposits, and is known as hydraulicmining. A smaller scale version of the same method isplacer mining, and both may have been used to work

alluvial placer deposits next to the river Cothiitself, judging by a large aqueduct which tapped theriver a mile or so upstream, and enters the site at alow level compared with the other known aqueducts onthe site. The water supply of the aqueducts was alsoused for washing crushed gold ore, and also possiblydriving stamping mills for comminution of the ore(Lewis and Jones, 1969).

Figure3.Small tank (A) near north opencast

One of the first aqueducts was built at a high level onthe east slope of Allt Cwmhenog and tapped a smallstream about 2 miles (3 km) away. There is a large tankat its end, where it sweeps around the brow of the hillonto the west side of the ridge. A gold vein must havebeen discovered here, because there is a large opencastbelow the tank. Yet the larger and longer aqueduct(with a gradient of 1 in 800) taps the river Cothiabout 7 miles (11 km) to the north-east and traversesthe same opencast, so must be later in date.

By contrast, several tanks found on the site did notshow a vein, so were abandoned. The tank shown at rightoccurs not far from the north opencast and was probablyintended to find the limits of the deposit located inthe adjacent opencast (Tank A in the schematic diagram

below). It clearly didn't find the vein, and was thusabandoned. The water supply may have been obtained froma small leat run from a stream up the main Cothi valleybefore the much larger aqueduct was constructed.

Opencast mining

Figure4. Development of mine

Prospecting was successful and several opencasts arevisible below the large tanks built along its length.The only exception is the final and very large tank,below which are two reservoirs. It is likely that thiscomplex was used for washing powdered ore to collectthe gold dust.

More leats and tanks can be found below the line of themain aqueduct, some of which are shown on the map of

the site. They surround the lip of the very largeopencast and the tank shown at right is one which wasbuilt on the main aqueduct. It was successful infinding a vein, judging by the opencast below, but musthave been modified later to feed a washing table builtto the left-hand side (near the figure in the picture),probably to wash the crushed ore from the same opencastworking. It is labelled Tank C in the schematicdiagram. Similar tanks occur below as the Romansfollowed the large vein down to the road and the mainopencast. Most of the opencast workings must thereforebe Roman in origin, since one of the aqueducts has beenconfirmed by carbon-14-dating as to predate all modernworkings. Just by the road itself the Carreg Pumsainthas been erected in the space beside a large mound, nowthought to be a dump of waste material from miningactivities.

The existing ponds above and below the minor road fromPumsaint to Caeo, were probably part of a cascade forwashing ore, the upper tank having yielded largequantities of Roman pottery from ca 78 to at least 300AD (Lewis, 1977; Burnham 2004). The upper pool is knownas Melin-y-Milwyr, or the soldier's mill, an intriguingname that implies that watermills may have been usedhere during the Roman period. Alternatively, it mayhave been a sequence of washing tables for the crushedgold ore. A large-scale mill complex is known fromBarbegal in southern France, where no less than 16mills (in two lines of 8 each) were built into the sideof a hill and supplied with water from a singleaqueduct. There were two lines of parallel overshotmills, the outflow from one feeding the next below. Themill supplied flour to the region. Moreover, Roman

engineers used sequences of reverse overshot water-wheels to dewater mines, and the deep workings atDolaucothi produced a fragment of such a wheel duringthe 1930s when deep mining operations were resumed.Sequences of such wheels increased the lift, and oneextensive sequence of 16 wheels was found in old Romanmine workings on the Rio Tinto river in the 1920s. Thewheels were arranged in pairs and could lift waterabout 80 feet (24 m) from the bottom of the mine there.

OPEN PIT METHOD: Most of Australia's gold productioncomes from open-cut mines. Large capacity earth-movingequipment is used to remove waste rock from above theore body and then to mine the ore. Waste and ore areblasted to break them into sizes suitable for handlingand transport to waste dumps or, in the case of theore, to the crusher.

Underground mining is used where the depth of ore belowthe surface makes open-cut mining uneconomic. Verticalshafts and declines (spiral tunnels) are used to movepeople and equipment into and out of the mine, toprovide ventilation and for hauling the waste rock andore to the surface.

Deep extensions of deposits mined by open pit methodsmay be mined later by underground methods beneath theold open pit.

Processing: Coarse gold may be removed by gravityconcentration. The processing required to recover finegold from crushed ore is determined by the free-millingor refractory nature of the ore. Free-milling ore isore from which gold can be recovered by crushing,grinding and cyanidation (treatment with a dilute

cyanide solution) without additional processing. Free-milling oxide ores are suitable for direct cyanidationof the crushed and ground ore.

In refractory ore, gold is locked in the sulphideminerals so that, to achieve satisfactory levels ofgold recovery, additional processing such as roastingor biological leaching is required before cyanidation.Sulphide minerals in refractory ores are converted tooxides by either roasting or biological leaching torelease the gold. In biological leaching the oxidationis caused by the action of specific bacteria on theore. The tonnage of refractory ore to be roasted orleached is greatly reduced by first producing a finelyground concentrate.

Ground ore or treated concentrate is placed in a weaksolution of sodium cyanide, which dissolves gold andforms slurry of gold-bearing solution and barrensolids. Some ores may be treated by heap-leaching. Thisinvolves sprinkling a weak cyanide solution over anopen pile of ore stacked on an impervious base. Thesolution percolates through the ore, leaching gold asit goes, and is drawn off at the base before beingtreated to recover the gold.

In both cases, the gold is recovered from the gold-bearing solution in a process in which pellets ofactivated carbon made from charred coconut husks areadded to the slurry and the gold-bearing ions areadsorbed onto the pellet surface. The pellet load ismoved through a number of linked tanks containingslurry in a direction opposite to the slurry movement.

The pellets loaded with gold are removed and the goldis stripped from them by washing in a solution of hotcyanide. The carbon used in the process is recycled andan electric current is passed through the new solution,depositing the gold on a steel wool cathode. The goldladen cathode is treated with hydrochloric acid todissolve any residual steel and the gold sludge isfiltered and dried, ready for smelting. At this stagethe gold-bearing material may contain silver and basemetals.

Gold is smelted in a crucible furnace to produceunrefined bullion. In smelting, base metal impuritiesare oxidized and absorbed, leaving the precious metalsto be poured into ingot moulds. Smelted gold is thenrefined.

SLUICE BOXES: Riffle or sluice boxes were the mainmethods of recovering gold. Nicknamed Long Toms, thesewere long, terraced wooden boxes, over which gold-bearing gravel was washed. Each step of the box had alip that trapped the heavier gold and allowed thelighter materials to wash away. Eventually the heavygravel and gold caught in the terraces was washed up ina pan.

These methods all relied on water, without whichrecovering gold was impossible. At each of NewZealand’s goldfield’s there were small dams and waterraces – channels that cut across contours, bringingwater from creeks to areas where gold was worked.

SLUICING: Sluicing was a method where water was pipedinto successively narrower pipes leading to hoses (with

nozzles called monitors), which sprayed jets of waterstrong enough to kill a person. The jets were aimed atgravel faces and helped to wash gold-bearing gravelsdown through sluice boxes. In places like Bannockburnand St Bathans in Central Otago distinctive gravelpillars are a legacy of these giant water guns. Using asluice box to extract gold from placer deposits haslong been a very common practice in prospecting andsmall-scale mining. A sluice box is essentially a manmade channel with riffles set in the bottom. Theriffles are designed to create dead zones in thecurrent to allow gold to drop out of suspension. Thebox is placed in the stream to channel water flow.Gold-bearing material is placed at the top of the box.The material is carried by the current through the voltwhere gold and other dense material settles out behindthe riffles. Less dense material flows out of the boxas tailings.

Larger commercial placer mining operations employscreening plants, or trommels, to remove the largeralluvial materials such as boulders and gravel, beforeconcentrating the remainder in a sluice box or jigplant. These operations typically include dieselpowered, earth moving equipment, including excavators,bulldozers, wheel loaders, and rock trucks.

PLACER MINING METHOD: When it comes to gold mining,most of us will get our yellow metal by sifting throughsands and gravels along rivers and streams. This iscalled placer mining. It is due to the geological age

of the earth that this is even possible. All golddeposits started as hardrock formations...and stayedthat way until there were earthquakes, rivers,glaciers, tidal waves and a lot of earth movement whicheroded mountains and ground down the rock into itssmallest form; dust. Trapped in all this rock wereveins of gold, typically in quartz. These veins werealso pulverized down into small pieces in nugget, flakeand flour size. Because gold is so heavy, it settles tothe bottom of our rivers, streams and any deepdepression or crevice. This is where placer miningcomes in. When we sift through all this sand and gravelto separate the gold, we are actually looking back atthe earth's history. I know, I know, that's nice; nowshow us a faster way to get at this gold.

The quickest way to reach this heavy mineral is to godeep and that is the hardest thing we could possiblydo. Most placer gold is found within 50 feet of thesurface of the ground. That's the "easy pickens". It isall the piles of gravels and sand we have to move firstbefore we can reach the heavy nuggets. All thisunwanted material is called "over burden" and it is theover burden that will make or break a mine. There aresome very rich areas containing coarse gold thattravels for miles following the bedrock of the earth,but there are just too many feet of rock and assortedmineral debris sitting on top of it to make itworthwhile to mine. This is just one of the reasons Iam developing the deep gold drill to reach these zonesof wealth that no one else can reach.

These golden rich layers vary in thickness from 18"down to a thin hair like trace. If we were to trace

back to where these layers started from, it would be anintrusive outcropping of very rich veins that have beencrudely eroded and strewn across bare rock or beengiven enough time to settle to bedrock. Glaciers andtremendous earth movements have left these rich zonesburied deeply with over burden. California has one ofthese very rich areas. The surface of which has beenthe ancient streambeds that were worked in the goldrush of 1848 to 1855 (1849 being the height of thisrush). These semi-surface ancient streams were oftenmined with hydraulic mining techniques. Please keep inmind that these mined areas often had 40 feet ofunwanted rock sitting on top of them and were up amountain side nowhere near water. That is one view ofwhere gold was. The other is the heavy rich layer thatsits on bedrock down deep under the earth. Some ofthese bedrock areas were accessible by miners usuallyby diverting rivers and digging down to the heavylayer.

Every method was employed to extract the wealth. Goldpanning, sluicing, dredging and hydraulic mining wereall used to good effect. Some outcroppings of hard-rockgold were also found. At the time, crude attempts atcrushing this mostly quartz rock were used to try tofree the yellow treasure from the parent rockformations.

This crushed slurry was washed into massive sluiceboxes and a lot of gold was captured. Using this earlymethod only captured about 70% of this mineral wealth.

SHOVEL, PAN AND CRADLE: Gold mining was rough, physicalwork. Where alluvial gold was very rich, it could be

obtained with a shovel and pan. However, pans were usedmainly for prospecting. Simple machines known ascradles (often made from wooden liquor boxes) wererocked back and forth – the heavier gold collecting onmatting on the cradle base.

Engineering was also used to expose river beds. TheOxenbridge tunnel on the Shotover River and the damgates across the source of the Kawarau River drainingLake Wakatipu at Frankton are the two most famousexamples. Both were spectacular failures – little goldwas found in the exposed bed of the Shotover once waterwas diverted through the tunnel. And when the Kawaraudam gates were closed they had little effect on waterlevels downstream.

Hard-rock mining: Hard-rock mines followed quartzveins, which contained gold. Underground mining wasvery expensive as tunnels had to be blasted and theroofs supported. Mines such as those at Waihi onCoromandel Peninsula and Waiuta on the West Coastfollowed reefs until they became too deep or low gradeto be mined economically. The recovered quartz wascrushed by stamper batteries, and cyanide was used toreclaim the gold.

PLACER MINING: Placer mining is the technique by whichgold that has accumulated in a placer deposit isextracted. Placer deposits are composed of relativelyloose material that makes tunneling difficult, and somost means of extracting it involve the use of water ordredging.

Gold panning is mostly a manual technique of separatinggold from other materials. Wide, shallow pans are

filled with sand and gravel that may contain gold. Thepan is submerged in water and shaken, sorting the goldfrom the gravel and other material. As gold is muchdenser than rock, it quickly settles to the bottom ofthe pan. The panning material is usually removed fromstream beds, often at the inside turn in the stream, orfrom the bedrock shelf of the stream, where the densityof gold allows it to concentrate, this type calledplacer deposits.

Gold panning is the easiest and quickest technique forsearching for gold, but is not commercially viable forextracting gold from large deposits, except where laborcosts are very low or gold traces are substantial.Panning is often marketed as a tourist attraction onformer gold fields. Before large production methods areused, a new source must be identified and panning isuseful to identify placer gold deposits to be evaluatedfor commercial viability.

DREDGING: Although this method has largely beenreplaced by modern methods, some dredging is done bysmall-scale miners using suction dredges. These aresmall machines that float on the water and are usuallyoperated by one or two people. A suction dredgeconsists of a sluice box supported by pontoons,attached to a suction hose which is controlled by aminer working beneath the water.

State dredging permits in many of the United Statesgold dredging areas specify a seasonal time period andarea closures to avoid conflicts between dredgers andthe spawning time of fish populations. Some states,

such as Montana, require an extensive permittingprocedure, including permits from the U.S. Corps ofEngineers, the Montana Department of EnvironmentalQuality, and the local county water quality boards.

Some large suction dredges (100 horsepower (75 kW) &250 mm (10 in)) are used in commercial productionthroughout the world. Small suction dredges are muchmore efficient at extracting smaller gold than the oldbucket line. This has improved the chances of findinggold. Smaller dredges with 50-to-100-millimetre (2 to4 in) suction tubes are used to sample areas behindboulders and along potential pay streaks, until "color"(gold) appears.

Other larger scale dredging operations take place onexposed river gravel bars at seasonal low water. Theseoperations typically use a land based excavator to feeda gravel screening plant and sluice box floating in atemporary pond. The pond is excavated in the gravel barand filled from the natural water table. "Pay" gravelis excavated from the front face of the pond andprocessed through the floating plant, with the goldtrapped in the onboard sluice box and tailings stackedbehind the plant, steadily filling in the back of thepond as the operation moves forward. This type of goldmining is characterized by its low cost, as each rockis moved only once. It also has low environmentalimpact, as no stripping of vegetation or overburden isnecessary, and all process water is fully recycled.Such operations are typical on New Zealand's SouthIsland and in the Klondike region of Canada.

3.Identify 10 solid minerals found in Nigeria andstate their economic significances.

ANSWERS

I. COLUMBITE AND TANTALITE: Columbite and Tantalite areores used to produce the elements niobium and tantalum.Columbite and tantalite are collectively known ascoltan in Africa. Tantalum is a valuable rare elementused in electronics manufacturing. In Nigeria,pegmatite deposits of coltan are frequently also thesource of several precious and semi-precious stonessuch as beryl, aquamarine, and tourmaline. Thesepegmatites are found in Nassarawa State near the JosPlateau, as well as in several areas in southeastNigeria. There is small- scale mining of theseminerals.

II. IRON ORE: Nigeria has several deposits of iron ore,but the purest deposits are in and around Itakpe inKogi State.

The National Iron Ore Mining Company was founded in1979 and given the mission to explore, exploit,process, and supply iron ore concentrate to theAjaokuta Steel Company (ASCL) in Ajaokuta and DeltaSteel Company (DCL) in Aladja. Additional demand hascome from several steel rolling mills. The company andits mining operations are based in Kogi State. Exportof excess iron ore beyond what is required for domesticneeds is currently being explored. Additionally, the

Nigerian government has invested in foreign iron oreoperations in Guinea.

III. COAL: Drilling has indicated reserve of 189milliontones in the lower coal measures of Benue state and32million tones in Agwu Ndeabo shale group at Obi nearLafia in Pleateau state. Thus, seams of coal are knownto occur at Lamja in Adamawa state. Coal reserve alsoproved in Anambra state, Enugu state.

IV. MARBLE: Large reserves of high grade of marble areavailable in Jakura and Ubo in Kwara state. Magneriamarble occurs at Itobe in Benue state, at Elebu inkwara state, at Burum in FCT, Abuja. Also at Igbeti inoyo state.

V. GYPSUM: Gypsum is an important input for theproduction of cement. It is also used for theproduction of Plaster of Paris (P.O.P) and classroomchalks. A strategy for large-scale mining of gypsumused in the cement industries is urgently required tosustain the existing plants and meet the futureexpansion. Currently, cement production is put at 8million tonnes per annum while the national requirementis 9.6 million tonnes. About one billion tonnes ofgypsum deposits are spread over many states in Nigeria.

VI. TALC: Over 40 million tonnes deposits of talchave been identified in Niger, Osun, Kogi, Ogun andKaduna states. The Raw Materials Research andDevelopment Council (RMRDC)’s 3,000 tonnes per annumcatalytic plant is the only talc plant in the

country. The talc industry represents one of the mostversatile sectors of the industrial minerals of theworld. The exploitation of the vast deposits wouldtherefore satisfy local demand and that for export. VII. LIMESTONE: Limestone occurs in Northern Nigeria,Western Nigeria, Eastern Nigeria and some various zonesin Nigeria. Large reserve of good quality limestone hasbeen found in Igumale, Ogboluka and Yander in BenueState. Thin limestones are suitable for formation ofcement. Crystalline limestone has been found in Kwakutiin Niger state. They have also been found in okpella,Edo state, also in Ewewkoro in Shagamu and other partof ogun state. Large reserves of limestone have beenproved in Nkalagu near Enugu. They have been widelyused for the production of cement, buildingconstruction.

VIII. CLAY: clay suitable for the manufacture of glacedceramic particle are found near Jos at Dakingean and inKaoje in sokoto state, at Garkida in Adamawa state, andKankaro in Kaduna state. Fine clay occurs associatedwith one of the seams at Enugu. Also in the manufactureof bricks.

IX. URANIUM: The Nigeria Uranium Mining Company (NUMCO)was a parastatal organization that controlled theexploration and mining of uranium in Nigeria and was apublic/private partnership with Total Compagnie Minièreof France, which owned 40% of the company. In 1989,Total pulled out of the partnership, and in 1993 thegovernment reassigned NUMCO's responsibilities to the

Nigerian Geological Survey. The NUMCO Corporation wasdissolved in 1996, and the government is in the processof liquidating its remaining assets.

Recently, several important uranium deposits werediscovered in Cross River State, Adamawa State, TarabaState, Plateau State, Bauchi State, and Kano State bythe British Geological Survey.

X. I. GOLD: Gold deposits are found in NorthernNigeria, most prominently near Maru, Anka, Malele,Tsohon Birnin Gwari-Kwaga, Gurmana, Bin Yauri, Okolom-

Dogondaji, and Iperindo in Kwara Stateit is not verydominant in the country.

Gold production began in 1913 and peaked in the 1930s.During the Second World War, production declined. Mineswere abandoned by colonial companies, and productionnever recovered.

The Nigerian Mining Corporation (NMC) was formed in theearly 1980s to explore for gold. Lack of funds and thelure of easier profits from oil production led to itsfailure. There is no large scale gold mining operationin Nigeria today, though there is small-scale miningcarried out by artists.

The family of Aleye from Anka is one of the leadinggold families in the region.

Economic importance of gold. Gold has long been amedium of exchange and investment. It is widely used to

produce coins such as the Australian Nugget. AlthoughGovernments of most countries include holdings of goldas part of their monetary reserves many are starting toreduce their holdings. Financial institutions andindividuals also use gold as a store of wealth.

The main uses of gold are jewellery, dentistry, theadornment of buildings and for artistic purposes. Injewellery, gold is often mixed with other metals toproduce alloys of different colours. White gold is analloy of gold with silver, palladium, nickel andcopper. Yellow, green and red golds are produced byalloying gold with copper and silver in differentproportions. The gold content of jewellery is expressedas a number of carats - pure gold is said to be 24carat gold; 18 carat gold contains 18/24 or 75% puregold.

High electrical conductivity, malleability andductility favour the use of gold in electronic andcomputer circuitry, radar equipment and satellites.Because of gold's heat reflecting properties it wasused as a film coating on the Apollo 14 lunar module,the vehicle which first landed man on the moon. Animportant and growing use is in the mechanism andcircuitry of safety air bags in motor vehicles.