Chapter 4 Flashcards
Where are most diamonds mined coming from?
From primary deposits
In which deposits diamonds are more concentrated?
In secondary deposits.
Which deposits contain a higher percentage of gem quality diamonds?
Secondary deposits.
Where geologists focus search for primary deposits?
They focus on cratons.
Where geologists look for secondary deposits?
They look for deposits in rivers, streams, and estuaries flowing away from cratons.
What helps geologists narrow the search areas for diamonds?
Various surveys.
What kind of deposits require more bulk sampling than primary deposits to asses potential diamond content?
Secondary deposits.
How open-pit mining works?
Open-pit mining removes diamond-bearing ore from a large opening dug at the surface of the earth.
What is most common method of underground diamond mining.
Cave mining.
What are three main steps of diamond recovery?
Sizing, concentrating, and recovering.
How is sizing accomplished?
Through a series of crushing and scrubbing.
What was cause of shift in emphasis from secondary to primary diamond mining?
Improved technology.
Where are largest known marine deposit in the world?
In Namibia.
In how many regions the majority of diamonds are produced?
In four main regions.
Where are located most diverse diamond sources?
In Africa.
Which country is a top diamond producer in terms of both value and volume?
Botswana.
Which mine was once a major colored diamond producer?
Australia’s Argyle mine.
Who is the 3rd largest diamond producer?
Canada in terms of both volume and value.
From which deposits diamonds are mined in Brazil?
Alluvial deposits.
How much rough diamonds Russia provides?
Russia provides about a third of the world’s supply.
Definition of Alluvial deposits?
A deposit where gems are eroded from
their source rock and then transported away from the source and further concentrated in rivers and streams.
What is bulk sampling?
Large scale character sampling of 5,000 to 10,000 tons.
What is cave mining?
An underground mining technique in which orebody is drilled beneath the surface, loosened, and collected as it falls.
What is character sampling?
Testing the size, shape, clarity, and color of diamonds in a deposit based on 500 tons of rock.
What is dense media separation?
A recovery process that separates diamonds from lighter materials.
What is a drift?
A horizontal tunnel drilled through diamond pipe.
What is geochemical testing?
An analysis that determines the chemical composition of the sample
What is a mechanism that uses diamond’s affinity for grease to separate diamonds from other minerals?
Grease belt
What are indicator minerals?
Minerals that form along with diamonds at great depths and are brought to the surface by the same kimberlite or lamproite.
Definition of marine deposit?
A secondary diamond deposit created by rivers or streams carrying diamonds to the shoreline or ocean floor.
What is micro diamond testing?
Screening for the presence of tiny diamonds in a sample.
Definition of ore grade?
The concentration of diamonds in a deposit, measured by the amount of diamonds in 100 tons of earth removed
What is overburden?
Rock or soil that covers a diamond-bearing orebody.
What is a parcel?
A quantity of stones, sometimes of similar size and quality, packaged together for sale or storage.
How do you call a deposit where gems are found in the rock that carried them to the surface?
Primary deposit.
Definition of recovery?
A process used to separate diamonds from host rock or sediments.
Definition of secondary deposit?
A deposit where gems are found away from their primary source.
How is called vertical tunnel drilled in stable rock near the pipe to provide access for personel, equipment, supplies and ventilation?
Shaft.
How is called a process to reduce diamond bearing ore to smaller, more manageable sizes?
Sizing
What is X-ray separation?
A rough recovery method that uses X-rays to detect diamonds and an air jet to remove them from ore.
What many mining companies do to find diamonds?
They use advanced technology to find and mine diamonds.
What modern mining involves?
Extensive exploration, strategic evaluation, and sophisticated construction and operation.
Why large mining companies such De Beers and ALROSA invest a large amount of their revenue in exploration each year?
Even newer mines will eventually stop producing and need to be replaced in order to maintain the world’s diamond supplies.
What is first part of the mine to market journey?
Locating a diamond deposit.
What determines the exploration methods geologists use?
Type of deposit they are looking for.
What most people don’t realize about bringing diamonds to retail?
They don’t realize the time and money that was invested and the many tons of rock excavated to bring diamonds to store.
How alluvial deposits form?
They form when pipes erode and their rough diamonds wash into rivers or streams.
Where diamonds may accumulate in alluvial deposits?
In areas of slow water, such as river bends.
What happens if the speed of water in the rivers/streams is high enough?
Diamonds might be carried all the way to the ocean and form marine deposits.
Are kimberlite and lamproite stable in the earths atmosphere?
No they aren’t, environmental forces break them down relatively quick.
Where is example of onshore mining operation of diamonds?
Along the coast of Namibia.
What happens when diamonds are carried in river?
Diamonds are caught in small whirlpools and sink to the bottom.
Can alluvial deposits be found in dry places?
Yes in in places where rivers or streams once existed.
Where ocean currents deposit diamonds?
Offshore or wash them back onto the beach.
Why marine deposits contain higher percentages of high quality gem crystals then pipes do?
Because low-quality diamonds, with their inclusions and fractures, don’t survive the stresses of the marine environment.
Who and what kind of experiment conducted to show why marine deposits contain higher percentages of gem quality diamond crystals?
De Beers researchers conducted experiment in which they filled large cylinder with 265 pounds of steel balls, some gravel, water, and natural industrial diamonds. Then they rotated cylinder to simulate the tumbling similar to one that takes place in an onshore or tidal environment. After 7 hours the industrial diamonds were reduced to a fine powder.
What happened when De Beers researchers conducted “tumbling” experiment with gem-quality diamonds?
After 950 hours of tumbling, diamonds were still mostly whole, they had lost only 0.01 percent of their weight.
What you can say about exploration for diamonds?
Exploring for diamonds is a long, difficult, and expensive process. Mining companies spend millions of dollars each year.
How much time it takes from beginning a search to mining the first diamonds?
Usually more then 10 years.
What happens in first years?
The deposit is located and assessed for diamond content.
How long time takes building the mine before operations begin?
It takes several years.
What is Clifford’s Rule based on?
Its based on the observation that diamond-bearing kimberlites are associated with old cratons that have been stable for 2,5 billion years.
Who proposed Clifford rule?
T.S. Clifford in 1966.
What Clifford Rule states?
The rule states that although not all kimberlites contain diamonds, those that do occur only on these very old cratons on to of deep mantle keels.
Is Cliffords Rule holds true?
Largely yes, nearly all diamond-bearing kimberlites have been found on cratons or their margins, and most occur in the oldest cratonic areas.
Are the exceptions to the Clifford’s Rule?
Yes, like Argyle deposit in Australia and Lomonosov deposit in Russia
Why diamond deposits occur outside of cratons and away from their margin?
Plate tectonics and continental drift push younger rocks up to the much older cratons in collision belts.
Can kimberlites be located in collision belts?
Yes, but it’s more common for lamproites to occur here.
Where was located Argyle mine deposit?
It is located in a collision belt surrounding the Kimberley Craton.
What means diamondiferous?
Diamond-bearing
What is exception to Clifford’s Rule?
Lamproites deposits.
What method allows geologists to locate cratons?
Geological mapping
How sound waves works in geological mapping?
A craton is denser than the younger surrounding rock, so when a sound wave strikes it, the wave moves faster. When rapid wave movement is detected, scientists can be fairly certain that they have found a craton.
How are targeted secondary deposits by geologists?
Geologists look for ancient or current streams, rivers, and estuaries (tidal mouths of rivers) flowing away from cratons, or those that are located on direct paths from or near known kimberlite or lamproite pipes.
What type of diamond deposits are mostly mined in Sierra Leone?
Alluvial deposits.
Where alluvial diamonds are found?
In lakes, rivers, shoreline marine deposits, dried-up waterways, and offshore deposits.
Which deposits are easier to find?
Alluvial deposits because they’re above ground and often spread over large areas.
What does traditional artisanal mining exploration consist of?
Traditional artisanal mining exploration consists of sampling stream sediments or sediments of dried-up ancient riverbeds.
What types of sediments are sampled during traditional artisanal mining?
Stream sediments or sediments of dried-up ancient riverbeds.
How do prospectors use sieves in the process of artisanal mining?
Prospectors use large sieves and swirl the water around.
Why do prospectors swirl water around when using sieves?
Prospectors use large sieves and swirl the water around to make diamond and other heavy minerals sink to the bottom of the pan, while lighter materials float toward the edge.
What happens to lighter materials during the sieving process?
Lighter materials float toward the edge.
What do prospectors do after upturning the sieve?
To inspect the center of the sediment for any diamonds or indicator minerals.
Where do prospectors typically inspect for diamonds or indicator minerals?
They inspect the center of the sediment.
What do prospectors do if diamonds are found in a specific area? (alluvial)
If diamonds are found, they might work this area before moving to the next bend in the river.
What actions do prospectors take if only indicator minerals are found?
If only indicator minerals are found, they follow these upstream in hopes of finding diamonds.
Do artisanal miners typically work alone or in groups?
These types of miners tend to work on their own or in small groups.
What is the typical quality of diamonds found through traditional artisanal mining?
Quality of the diamonds might be high.
How does the quantity of diamonds compare to their quality in artisanal mining?
The quantity tends to be low.
What are modern exploration methods for alluvial deposits?
There are several methods: aerial photography, satellite imaging, and radar.
What are more traditional exploration methods for alluvial deposits?
Field mapping, soil sampling.
What are exploration methods for offshore deposits?
Giant pumps dredge up sediments from the ocean bottom for testing.
Why in late XX century focus turned to marine deposits?
Because of the huge quantities of diamonds in offshore deposits.
What is an example of diamond mining vessel ship operated in Namibia?
The Mafuta operated by Debmarine Namibia, a joint venture between DeBeers and the Namibian government.
How much of ocean floor Mafuta will scour?
6,000 square km
What alluvial deposit exploration often uses?
Mineral sampling.
How gravity surveys work?
Density variations is measured in the ground to detect kimberlite or lamproite, because they have more gravitational pull than surrounding rock.
What for aerial photography and digital topography are used?
To look for circular or near-circular features in the landscape that could be pipes.
What aerial surveys can spot that would be not obvious to geologists on the ground?
Shadows and contours.
What have seeing an aerial surveyor in Canada for example?
Round shadow at the bottom of a lake that turned turned to be the top of a diamond-bearing pipe.
What can detect the possible presence of kimberlite pipes before ground exploration begins?
Aerial magnetic surveys.
How Aerial magnetic surveys work?
It maps out grid of back-and-forth passes to follow in order to cover the area thoroughly.
How electromagnetic surveys can be done?
It can be done on foot or from the air.
What happens after electromagnetic surveying a large area?
Map is generated showing various features not visible to geologists.
How information from surveys helps geologists?
It helps further narrow the targeted areas.
How modern advances helped in exploring deposits?
They have assisted in the discovery of diamond deposits in previously unexplored areas.
How magnetic surveys on foot are taken?
Typically, a person holding a handheld GPS moves along a predetermined path and takes a reading every 50 meters. The data is saved and carefully studied for signs of magnetic variations.
How seismic survey works?
Seismic surveys work similarly to magnetic and electromagnetic surveys but use sound waves to detect the features of different rocks.
Why kimberlite and lamproite have unique features?
They posses unique features that are detected by seismic surveying.
What geologists do after finding area to test?
They focus their search more precisely and look certain minerals, called indicator minerals. Sometimes minerals are discovered prior to surveying.
Why indicator minerals are important?
Because they either form in kimberlite or lamproite.
What the presence of indicator minerals often means?
That a pipe is not far away.
How far were indicator minerals transported by ancient glacial deposits from their original source in some Canadian mines?
300 km away. Still their paths were traced back to the kimberlite pipes
Why hand sorting heavy minerals concentrate in the search for indicator minerals is best?
Because human eye can detect subtle shapes and colors that an automated process would miss.
Which indicator minerals collected in Canada helped locate important diamond-bearing kimberlite pipes?
Diopsides and garnets.
How the termite mounds can help in the search for diamonds?
Termites carry underground minerals to the surface while digging their tunnels. In termite mounds geologists have found diamond indicator minerals, and it lead to discovery of diamond pipes.
What is critical step in the search for diamonds?
Mineral sampling.
What are vital clues from mineral sampling?
Mineral’s age, how far it’s from source, and how it got there.
Why geologists try to test as wide area as possible with a few samples as possible?
To save time and money.
List indicator minerals found in association with kimberlite and lamproite?
Red and orange garnet, black spinel, diopside, olivine, limenite, chromite, and perovskite, tiny diamonds.
What is especially helpful when found in mineral sampling?
Tiny diamonds, because they indicate that source deposit is probably nearby.
When few or no indicators minerals found is exploration finished?
No, geologists further explore areas identified as potentially diamond bearing.
What was the case with Canada explorations?
The explored area had being subjected to substantial weathering and erosion by glaciers, the indicator minerals had been broken up, and the top of the kimberlite pipe was buried under the glacial deposits.
What is analyzed in geochemical testing to determine the presence of specific elements derived from indicator minerals in the samples?
Samples of rock, soil, or even vegetation in the targeted area.
What typically prompts further exploration and testing of samples in areas with alluvial diamond deposits?
The discovery of diamonds is typically what prompts more exploration and testing of samples in these areas.
What happens after locating a deposit, primary or secondary?
Geologists begin testing for the presence and concentration of diamonds.
What is required for testing for presence and concentration of diamonds?
This testing require increasingly larger samples, which are more expensive and more difficult to obtain.
Which stage of exploration is critical to determine whether a project is continued or abandoned?
Testing for the presence and concentration of diamonds.
What is order of sampling during testing deposit viability?
Microdiamond testing, Character Sampling, Bulk Sampling
How big parcel of diamonds requires bulk sampling to asses quality of large-scale secondary deposit?
Because secondary deposits tend to be wider and shallower than pipes, it’s typically required parcel of 3,000-5,000 ct diamonds.
How big parcel of diamonds requires bulk sampling for accurate evaluation of primary deposit?
2,000 ct diamonds
How are gathered samples for microdiamond testing of primary deposits?
They are gathered from drilling cores.
How are gathered samples for microdiamond testing of secondary deposits?
They are gathered from river gravels or seafloor sediments.
How samples from microdiamond testing are sorted?
The samples are hand sorted under a microscope.
What is needed for character sampling?
For character sampling, blasting and large excavators will be needed
What gives a general idea of diamond, size, shape, clarity, and color?
Character sampling.
What helps scientists develop indication of diamond quality and determine ore grade?
Character sampling, processing of up to 500 tons of earth.
How is measured concentration of diamonds during character sampling?
It’s measured by the amount of diamonds in 100 tons of rock.
When testing progresses from character sampling to the last stage, bulk sampling?
If results are promising.
Is it usually enough to analyze one character sample?
No, usually it’s necessary to analyze multiple character samples from one deposit.
To what bulk sampling is similar?
It’s similar to character sampling, but on a much larger scale.
How big parcel of diamonds during bulk sampling needs to be produced for an accurate evaluation?
A diamond parcel of about 2,000 carats.
To what process bulk sampling on-site operations are similar?
It’s the same as if a small mine were in production.
What about mining company must be knowledgeable about?
Company must be knowledgeable about local geology but also mindful of the local environmental and economic issues.
When Davik mine transitioned fully to underground mining?
In September 2012.
What is basic approach to mining a primary deposit?
It is to dig out and remove all the material in and around the pipe.
How is usually accomplished mining primary deposit?
By open pit mining followed by underground mining.
How digging an open-pit mine usually begins?
With the removal of layers of overburden - rock or soil - that cover the pipe.
What miners do with overburden?
They process it for any diamonds it main contain.
What is characteristic of overburden?
Overburden is highly weathered, so it’s soft and easy to work on.
How overburden is called by miners?
Yellow ground.
How is called the hard rock below the overburden?
Blue ground.
What miners do in first?
They drill holes into the pipe, insert explosives into holes, and blast the ore loose.
What kind of explosives are used by miners?
Low-velocity charges to avoid shattering the diamonds.
What miners do after blasting the ore?
They remove the loosened material with hydraulic shovels and load it into large ore trucks.
What is true image of modern mining?
Most operations are large in scale (small towns size) and extremely expensive. Many Mines are highly mechanized. Miners use sophisticated remote-controlled devices and heavy machinery.
What forms as an open mine is developed?
It forms a deepening cone that follows the contours of the diamond pipe.
What is done to provide stability of pit so that wall doesn’t collapse and cause a landslide?
Sides are terraced to provide stability.
What terraces in pit also provide except stability?
Terraces also provide roadways around the mine’s perimeter for the ore trucks.
Where the trucks carry rock to?
To the processing facility, where the diamonds are recovered from the ore.
From what depth of an open-pit mine depends?
It depends on the characteristics of the pipe and the economics of the mining operation.
What happens as the pit deepens?
The quantity of diamonds decreases and it becomes much narrower and more difficult fot the giant trucks to move in.
Why widening of narrow pit is uneconomical?
Because rock doesn’t contain diamonds.
What happens if the diamond-to-ore ratio is still good in the pipe, but it’s to narrow?
Mining company may consider developing an underground mine.
What an underground mine consist of?
A series of vertical shafts and horizontal tunnels (drifts) in and around a pipe.
Where are shafts drilled?
They are drilled in stable rock near the pipe to provide access for personnel, equipment, supplies, and ventilation.
Where are drifts drilled?
Drifts - horizontal tunnels - are drilled from the shafts through the pipe to extract ore.
What kind of underground mining diamond method is most common nowadays?
Cave mining
What is cave mining?
Cave mining is the method where the orebody is drilled beneath the surface and recovered as it falls.
Why cave mining is most common technique today?
This technique is more mechanized, so it requires a smaller work-force.
Is there one category of cave mining?
There are many subcategories, but they all follow same principles.
How drifts are build in cave-mining method?
Concrete-lined tunnels are built directly under a large section of ore.
How explosives are placed in orebody in cave mining technique?
They are placed in the orebody at evenly spaced openings in the tunnel ceiling.
What happens when in cave mining method explosives detonate?
Low-velocity detonation loosens the ore, which falls through the openings. This leaves the a void in the rock, which causes the overlying kimberlite to fracture under its own weight.
(Cave mining) What happens after kimberlite falls through openings?
This eventually causes the ground at the surface to settle or collapse and some of the wall rock to fall into the pit.
Why cave mining is safer than traditional underground mining?
Because the orebody is collected when it falls after blasting and requires a much smaller workforce because much of the work can be automated.
(cave mining) What is next step of operation after broken ore falls through opening?
Miners use heavy equipment to scrape ore out of the tunnel, and load it into cars on electric trains or conveyor belts that dump it into an underground crusher.
(cave mining) Where ore goes from the underground crusher?
A conveyor system carries the ore to buckets that take it up a vertical shaft to the surface for further processing.
What happens once ore is excavated?
It goes through a diamond extraction process, called recovery.
How the sizing is accomplished?
In a series of crushing and scrubbing operations to reduce ore size to a couple of inches.
How strong is interface between ore and the diamonds?
It’s weak, so crushing easily releases the diamonds.
What is the disadvantage of crushing process?
Crushing limits the size of rocks or diamonds that remain intact. Rough exceeding those limits might be destroyed.
What most mines do to prevent large diamonds passing through the crushers?
They use detection systems that automatically stop the conveyors.
Which anti-crushing detection systems are most powerful and effective?
X-ray detection system, but each mine has its own system.
What happens with kimberlite fragments after leaving scrubber?
They are washed with water as they flow from scrubbers. Any fragments larger then the sieve holes will go to secondary crushing.
How X-Ray separation process works?
A thin stream of ore passes in front of an intense X-ray beam, a diamond crystal emits light that triggers a jet of air that blows the stone away into a collection bin.
How dense media separation works?
The ore is mixed with liquid and fed into a cone-shaped container /cyclone/. The cyclone spins the mixture, forcing liquid to and diamond-bearing material downward.
What kind force is used in dens media separation?
Centrifugal force.
How grease belt works?
As water washes the ore over the grease belt, diamonds embed in the grease belt. The grease will be melted away, leaving the diamonds.
What happens after primary crushing?
Scrubbers wash and tumble the ore to remove dirt and clay. The the ore is typically passed through a screen to check the size.
What happens when the ore that is to large after primary crushing, washing/scrubbing and screening?
Ore go again through crushing and scrubbing again, until they are small enough for the next step: concentrating.
How is differently called dense media separation?
Heavy media separation.
What happens with lighter material in dense media separation?
It floats to the top.
What happens with denser material in dense media separation?
It sinks to the bottom of the container.
How is separated material from liquid after dense media separation?
Rotating dryers evaporate the liquid.
How recover process can be accomplished?
It can be accomplished by different methods, most common are grease belt and X-ray separation.
What kind of affinity diamond has?
For grease and oils.
When and by whom X-ray separation method was invented?
In 1958 by Soviet scientists.
On what principle X-ray separation process in based?
On the fact that diamonds almost always fluoresce when exposed to X-rays.
Why diamonds must be sorted by hand after grease belt or X-ray separation process of diamonds?
Recovered material contains a high proportion of diamonds, but also other minerals too.
Enumerate the main steps of the recovery process?
Sizing, concentrating, recovery.
Enumerate steps of sizing?
Crushing, scrubbing, screening
Recovery steps?
X-ray separation, grease belt separation, hand separation.
Why Letseng mine is economic viable?
Because it’s ability to recover large stones intact.
What is largest D-flawless heart shaped diamond in the world?
The Graff-Venus 118,78-ct. Cut from 357-ct. rough recovered at Letseng mine 2015.
What did Gem Diamonds company did in Letseng Mine to minimize damage to large diamonds?
In mid 2013, the company replaced the crusher’s large steel jaws with a cone crushing system, where ore passes over a rapidly spinning cone.
What is the largest diamond found at Letseng mine in 2018?
Lesotho Legend 910-ct. D-colour rough.
Where are still used simple equipment and methods as the first diamond rushes?
In the Kono district in eastern Sierra Leone.
Where marine deposits are found?
They are found in the sand on beaches (onshore) or in offshore tidal zones.
For how long people have recovered diamonds from alluvial deposits?
For more than 2,000 years.
What percentage of diamond production is attributed to alluvial mining today?
Alluvial mining accounts today for about 15% of diamond production.
Why alluvial deposits may be more economical more for individual miners than large companies?
Many of alluvial deposits contain only small percentage of diamonds.
From where early alluvial diamond miners adapted their methods?
They adapted methods from gold miners.
Where did many veterans of the California Gold Rush of 1849 go after the word spread about the discovery of diamonds?
They went to Africa.
Are all alluvial mining is small scale?
No, but large-scale alluvial mining is rare.
What technology is used in large-scale alluvial mining?
Mechanized recovery and sieving and large earthmoving equipment, dams and dredging ships to pump diamond-bearing gravels, floating processing plant.
Is crushing is usual part of the recovery process for alluvial mining?
No, usually a series of sieves separates the diamonds from the surrounding waste material before they’re loaded into the washing pan.
Where is located Lucapa’s Lulo mine?
It’s located approx. 630 km east of Angola’s capital city, Luanda.
What is Lulo mine?
It’s a large alluvial diamond mine with a mining lease of over 3,000 sq. km in Angola.
Where Lulo’s diamodns are found?
Along 50km of the Caculo River in alluvial gravels.
What is the thickness of alluvial gravels in Caculo river?
0,2 - 1,5 m in thickness.
How far Lulo mine is from the largest diamond mine in the world?
It’s 150 km from Catoca mine.
Which X-ray technology is used by Lucapa in Lulo mine?
X-ray technology that can detect diamonds up to 1,100 ct.
What is the largest diamond mined in Angola?
The “4 de Fevereiro” diamond 404 ct.
What “4 de Fevereiro” name stands for?
It’s name is a reference to the Angola War of Independence.
What kind of diamonds is produced in in the Lulo mine?
Diamond of high clarity and colors, also pink and yellow diamonds.
Which alluvial mine is among of those having highest average rough price?
Lulo mine.
What method some onshore operations is sometimes used to dislodge diamonds trapped in small crevices?
They use large vacuums.
What methods are using mining companies for marine mining?
Various, these include modified alluvial large scale mining, shallow-water mining with divers, dee-sea operations with sophisticated, high-tech ships and vessels.
What is needed druing onshore mining and why?
Dislodging and and removing diamonds from small cracks and crevices requires special tools and procedures.
onshore in Namibia: What do miners do first to expose the seabed for diamond mining?
First, miners build large earthen dams in the surf zone to hold back water and leave the seabed exposed, up to 20m below sea level.
onshore in Namibia: What do miners do second to expose the seabed for diamond mining?
Large earthmoving equipment excavates and removes sand and gravel.
onshore in Namibia: How do workers ensure that diamonds are not left behind in the bedrock? (Step 3)
Then workers with brooms and other tools sweep out every crevice where diamonds might be hidden in the irregular, pockmarked bedrock. Sometime they use compressed air jets to dislodge diamonds trapped in small crevices.
What kind of vacuums some onshore operations use?
They use giant vacuums mounted on 10-ton trailers that follow earthmoving equipment.
Where is one of the world’s largest earthmoving projects?
In Namibia
What is the second type of marine mining?
Offshore diamond mining.
What poses an even greater recovery challenge compared to onshore diamond deposits?
Offshore diamond deposits pose even more of a recovery challenge than onshore deposits.
What analogy is used to describe the difficulty of offshore diamond mining?
Offshore diamond mining is a little like scattering a 900-g bag of sugar over two adjacent football fields, and then trying to to retrieve the sugar with a small vacuum on a dark night.
When Namibia’s onshore diamond resources are expected to run out?
By approx. 2035
What is the trend now in marine mining?
Trend is now developing to mine more offshore marine deposits as onshore mines near the end of production.
How offshore deposits are divided?
They are divided into 2 zones based on the depth.
How are diamond deposits mined in water less than 15 meters deep compared to deeper waters?
Deposits in water less than 15 m deep can be mined by divers, in deeper water, mining operations are more complex.
How divers work in shallow-water mining operations?
They use a hose attached to a suction pump located on shore or in a boat.
How the diver vacuums work?
The vacuum vacuums gravel off the ocean floor, the gravel from the pump is sieved, and the remaining material is sent to a plant for processing.
Why divers regularly return to explore areas that have produced diamonds in the past?
Because the surf constantly moves sand and gravel along the coast, possibly creating new diamond deposits.
What kind of vessels are used for deep-sea mining operations?
Large recovery ships, like Debmarines Debmar Atlantic.
How deep-sea mining operation begins?
With detailed mapping of the ocean floor.
What does Debmarine Namibia use to explore deep-sea ocean floor for diamonds?
Debmarine Namibia, a joint venture between De Beers and the Republic of Namibia, uses a state-of-the-art exploration vessel that scours 6,000 square km of ocean floor for diamonds.
What kind of equipment & methods are used for deep-sea mapping?
Mining companies use sophisticated equipment like sonar, along with data from global positioning satellites, to develop remarkably accurate maps of undersea floor.
How deep-sea mapping helps?
Generated maps help identify the areas most likely to contain diamond deposits, such as ravines, basins, and ridges.
Do divers take part in deep-see operations?
Yes
How work of divers look in deep-sea mining?
Divers use special heated diving suits, go down up to 40m deep, they use powerful vacuums to pick up material from the ocean floor.
How long diver can work deep-sea?
Diver can work for only short periods of time.
What some mining companies use to improve efficiency and reduce risk?
Some companies use automated crawlers equipped with devices that vacuum material from the ocean floor.
What is used for deposits at greater depths than 40m?
Large recovery ships are used.
What you can say about large recovery ships?
Each vessel is a self-contained unit and can operate in a variety of seafloor conditions.
How many ships operate in Debmarine Namibia company?
Debmarine operates a fleet of six ships, 19km off the coast of Namibia.
Till when Debmarine’s Namibia mining license will be valid?
Until 2035.
Which ship is the largest in Debmarine fleet?
The SS Nujoma
What was a cost of building SS Nujoma?
The cost $157 million in June 2017.
What size and weight is SS Nujoma?
113 m long and 12,000 ton heavy.
How much crew can be accommodated on SS Nujoma?
80 crew members.
What equipment is attached to the ship on the ocean’s surface during offshore diamond mining?
A horizontal crawler is attached to the ship on the ocean’s surface.
How does the crawler operate on the sea floor, and how are the dredged sediments transported to the ship?
The crawler moves along the sea floor to the targeted area and begins to dredge. The dredged sediments are pumped up to the ship via giant pipe.
How much sediment deep-sea crawler can collect per hour?
Up to 60 tons of sediment.
What happens with sediments when they reach the ship?
Sediments are pumped to the separation facility, where it is washed and sieved into smaller and smaller sizes.
What you can say about operation of Debmarina Namibia fleet?
These ships operate 24h/day, in depths up to 140m, in some of the most treacherous waters on earth.
What is the first step in processing the dredged material during offshore diamond mining?
First rotating drums crush larger rocks.
What happens to the sediment and crushed rocks after passing through the sieves?
They pass to the next stage, and oversized sediment is returned to the ocean.
How is sediment processed after being washed and sieved?
It goes to a dense media separation facility and is then processed for diamonds using X-ray technology.
What happens to sediment that does not contain diamonds?
Any sediment not containing diamonds is returned to the ocean.
What happens to the diamonds after they are separated from the sediments?
The diamonds are taken from the X-ray facility, sealed in an automated process, and put in small barcoded containers.
How are the diamonds transported after being sealed?
They are loaded into cases and flown via helicopter to the mainland three times a week.
