Ass #4 -Diamond Exploration & Mining Overview
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Questions and Answers

Which method involves analyzing the chemical composition of samples when indicator minerals are not located?

  • Character Sampling
  • Microdiamond testing
  • Seismic surveys
  • Geochemical testing (correct)

What is the purpose of the microdiamond testing stage in diamond recovery?

  • To determine the overall size of the deposit
  • To evaluate the clarity and color of diamonds
  • To perform geochemical analysis of soils
  • To find tiny diamonds in extracted samples (correct)

Which sampling method provides information about diamond size, shape, clarity, and color based on processing a large quantity of earth?

  • Bulk Sampling
  • Core Sampling
  • Geochemical Sampling
  • Character Sampling (correct)

What is assessed during the character sampling phase in the diamond recovery process?

<p>Physical characteristics of diamonds (B)</p> Signup and view all the answers

What is indicated when indicator minerals such as garnet or chromite are found during exploration?

<p>They signify the proximity to a diamond pipe (D)</p> Signup and view all the answers

Which method is commonly used for modern exploration of alluvial deposits?

<p>Aerial photography (D)</p> Signup and view all the answers

What is the primary characteristic of secondary diamond deposits?

<p>They formed from eroded primary deposits, resulting in higher diamond concentrations. (C)</p> Signup and view all the answers

Which of these statements best describes the location of most diamond-bearing kimberlites?

<p>They predominantly exist on ancient cratons. (B)</p> Signup and view all the answers

What is the significance of cratons in diamond exploration?

<p>They provide a denser substrate for sound waves indicating potential deposits. (C)</p> Signup and view all the answers

What technique involves analyzing soil for evidence of diamonds in exploration?

<p>Soil sampling (C)</p> Signup and view all the answers

What typically happens to heavily included diamonds during the secondary deposition process?

<p>They are broken down, leaving only higher-quality crystals. (C)</p> Signup and view all the answers

What is a significant factor that influences the strength of river currents in the secondary deposition of diamonds?

<p>The volume of water flow during different seasons. (A)</p> Signup and view all the answers

What is the estimated time frame to go from diamond exploration to the first mining of diamonds?

<p>Over 10 years (D)</p> Signup and view all the answers

What is the primary purpose of the sizing step in diamond recovery?

<p>To reduce ore size for easier management (D)</p> Signup and view all the answers

Which recovery method utilizes the property of diamonds to stick to grease?

<p>Grease belt separation (A)</p> Signup and view all the answers

In diamond mining, what is the significance of X-ray separation?

<p>It uses the fluorescence of diamonds under X-rays (C)</p> Signup and view all the answers

What distinguishes onshore marine mining from other mining methods?

<p>It requires special tools for dislodging diamonds (B)</p> Signup and view all the answers

Why has there been a shift from alluvial to primary deposits in diamond mining?

<p>Technological advancements made locating primary deposits more effective (A)</p> Signup and view all the answers

What is the primary mining method used in cave mining for diamonds?

<p>Drilling and blasting (D)</p> Signup and view all the answers

What is a notable characteristic of alluvial mining in terms of diamond production?

<p>It is not economical for larger mining companies (D)</p> Signup and view all the answers

How does marine mining differ from traditional land mining methods?

<p>It involves multiple methods including shallow and deep-sea operations (D)</p> Signup and view all the answers

What is the initial action taken when starting an open-pit mining operation?

<p>Removal of overburden covering the pipe (D)</p> Signup and view all the answers

What is the primary purpose of horizontal tunnels in an underground mine?

<p>To extract ore directly from the diamond pipe (C)</p> Signup and view all the answers

What type of charge is typically used to blast ore in open-pit mining to minimize damage to diamonds?

<p>Low-velocity charges (A)</p> Signup and view all the answers

How do the characteristics of an open-pit mine change as it deepens?

<p>The quantity of diamonds decreases and it becomes narrower (B)</p> Signup and view all the answers

What method is employed to create access for mining in an underground operation?

<p>Constructing a series of vertical shafts (D)</p> Signup and view all the answers

What is one method used in diamond exploration that involves the use of sound waves?

<p>Seismic surveys (B)</p> Signup and view all the answers

What is the main purpose of character sampling in diamond exploration?

<p>To provide an overview of diamond size, shape, clarity, and color (D)</p> Signup and view all the answers

Which method is commonly used to look for tiny diamonds in a rock sample?

<p>Microdiamond testing (D)</p> Signup and view all the answers

What type of surveys are widely used in diamond exploration to detect variations in magnetic response?

<p>Magnetic surveys (D)</p> Signup and view all the answers

Which indicator mineral is NOT commonly associated with kimberlite or lamproite?

<p>Quartz (B)</p> Signup and view all the answers

What is the primary process used in cave mining for removing ore?

<p>Allowing the ore to fall as it is drilled (A)</p> Signup and view all the answers

What is the role of the cyclone in the Dense Media Separation process?

<p>To create a centrifugal force that separates materials (C)</p> Signup and view all the answers

How does the grease belt method assist in diamond recovery?

<p>By allowing diamonds to adhere to grease while washing away other materials (A)</p> Signup and view all the answers

Which factor primarily differentiates alluvial mining from primary deposit mining?

<p>Alluvial deposits are typically more concentrated with diamonds (D)</p> Signup and view all the answers

What is a significant challenge of large-scale alluvial mining for larger companies?

<p>The low yield of diamonds per area mined (B)</p> Signup and view all the answers

What technique is most commonly used for marine mining operations?

<p>Deep-sea mining with high-tech vessels (A)</p> Signup and view all the answers

What is the main advantage of using modified alluvial mining methods?

<p>Ability to process large volumes of material quickly (C)</p> Signup and view all the answers

What is the primary mining technique used to extract diamonds from underground deposits?

<p>Cave mining (C)</p> Signup and view all the answers

What type of rocks are primarily associated with diamond formation?

<p>Peridotite and eclogite (D)</p> Signup and view all the answers

What is the most common source of blue color in diamonds?

<p>Boron (A)</p> Signup and view all the answers

Which of the following igneous rocks is much more commonly associated with diamonds?

<p>Kimberlite (B)</p> Signup and view all the answers

What is the primary condition needed for diamonds to form in mantle keels?

<p>Extreme pressures and temperatures (D)</p> Signup and view all the answers

How were diamonds primarily delivered to the Earth's surface?

<p>By transportation in kimberlite and lamproite (C)</p> Signup and view all the answers

What characterizes carbonado diamonds?

<p>They consist of many interlocking tiny diamond crystals. (B)</p> Signup and view all the answers

Which layer of the Earth is referred to as the 'crust'?

<p>The surface and outermost layer of the Earth. (C)</p> Signup and view all the answers

What is the primary geological process that brings diamonds to the surface?

<p>Eruption. (B)</p> Signup and view all the answers

What term describes the large, ancient, stable parts of Earth's landmasses?

<p>Cratons. (A)</p> Signup and view all the answers

Which of the following statements distinguishes metamorphic rock?

<p>It is formed through alteration by heat and pressure. (D)</p> Signup and view all the answers

What is a key factor in the formation of most diamond deposits?

<p>Proximity to cratons. (D)</p> Signup and view all the answers

What best defines the geothermal gradient?

<p>Rate of temperature increase with depth in the Earth. (D)</p> Signup and view all the answers

What is the primary component of carbonate compounds?

<p>Carbon and oxygen. (C)</p> Signup and view all the answers

Flashcards

Gravity Surveys

Measure density variations in the ground to find kimberlite or lamproite, indicating diamond deposits.

Magnetic Surveys

Measure variations in magnetic response to find kimberlite. A unique fingerprint helps pinpoint diamond-bearing rocks.

Electromagnetic Surveys

Use energy waves to find underground rock features helping locate diamond deposits.

Seismic Surveys

Use sound waves to map underground rock features in diamond exploration.

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Indicator Minerals

Minerals found near kimberlite/lamproite pipes. Their presence suggests diamonds might be nearby.

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Geochemical Testing

Tests rock, soil, or vegetation samples to identify specific elements linked to indicator minerals. Crucial for locating potential diamond-bearing kimberlites/ lamproites.

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Microdiamond Testing

Examines small diamonds in drill cores or secondary deposit samples to assess potential.

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Character Sampling

A deeper analysis, processing up to 500 tons of earth to assess diamond size, clarity, and colour.

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Ore Grade

The concentration of diamonds in 100 tons of rock. It measures the richness of the potential deposit.

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Cave Mining

A common underground diamond mining method where an orebody is drilled and extracted, leaving a large cave-like void that is then concrete-lined to form tunnels.

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Diamond Recovery - Sizing Step

The process of reducing large ore chunks to manageable sizes (a few inches).

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Dense Media Separation

A diamond recovery method separating diamond-bearing ore from waste materials using a heavy liquid and centrifugal force.

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Grease Belt Separation

A method of diamond recovery where diamonds stick to grease on a belt, separating them from other minerals.

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X-ray Separation

Diamond recovery using X-rays, as diamonds fluoresce (glow) when exposed to them.

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Alluvial Mining

A secondary diamond mining method, focusing on diamond deposits in riverbeds and sediments, now less common due to primary deposits.

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Marine Mining

Diamond mining in marine environments, including modified alluvial methods, shallow-water operations, and deep-sea methods with specialized ships.

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Primary Diamond Deposits

Diamond deposits found within the kimberlite or lamproite pipes that brought them to the surface.

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Secondary Diamond Deposits

Diamond deposits found outside the kimberlite/lamproite pipes, often in riverbeds, estuaries, or the ocean.

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Alluvial Deposits

Secondary diamond deposits found in riverbeds, where diamonds, being heavy, settle.

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Marine Deposits

Secondary diamond deposits in the ocean, where diamonds are carried by ocean currents.

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Diamond Exploration Time

The process of searching for and mining diamonds usually takes more than 10 years.

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Diamondiferous Deposits

Areas with diamond-bearing deposits, very rare compared to the Earth's crust.

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Clifford's Rule

The rule suggests that diamond-bearing kimberlites are primarily found on ancient cratons over deep mantle keels.

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Cratons

Ancient, stable parts of the Earth's continental crust.

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Sound Wave Exploration

A method used to study underground rock layers and structures by sending and analyzing sound waves.

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Modern Alluvial Exploration

Modern exploration methods for secondary deposits include aerial photography, satellite imaging, and radar.

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Cave Mining

A diamond mining technique where ore is drilled and extracted, creating a large cave-like space that's lined with concrete to make tunnels.

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Diamond Recovery - Sizing

Reducing large diamond ore chunks to smaller, easier-to-handle pieces (a few inches).

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Dense Media Separation

A diamond recovery method that separates diamond-bearing ore from waste using a heavy liquid and centrifugal force.

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Grease Belt Separation

A diamond recovery technique where diamonds stick to grease on a belt, while other minerals wash away.

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X-ray Separation

A diamond recovery method where diamonds glow under X-rays, allowing them to be separated from other materials.

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Alluvial Mining (Secondary)

A method of mining diamonds from riverbeds and sediments; less common than mining primary deposits.

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Marine Mining

Diamond mining in oceans, using various methods, including modified alluvial mining and deep-sea operations.

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Bulk Sample Size (Primary)

Between 5,000 and 10,000 tons of earth processed to evaluate a diamond deposit.

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Bulk Sample Size (Secondary)

A secondary deposit requires a larger sample (3,000-5,000 carats) than a pipe deposit for an accurate evaluation, due in part to its shallow and wide nature.

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Primary Deposit Mining Approach

Digging out all material around and in the pipe (kimberlite/lamproite) at a deposit.

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Open-Pit Mining

Removing overburden (rock/soil) from a diamond pipe, then removing the ore rock beneath. The ore often has a bluish color.

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Overburden

Layers of rock or soil covering the diamond pipe in an open pit mine. Usually yellowish.

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Blue Ground

Hard rock in an open pit mine, often containing diamonds, with a bluish color.

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Underground Mining

A method using shafts and tunnels to reach and remove diamonds in and around a pipe.

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Gravity Surveys

Method to detect diamond deposits by measuring density variations in the ground.

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Magnetic Surveys

Identifies diamond-bearing rocks by detecting variations in their magnetic response.

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Electromagnetic Surveys

Locates underground rock features using energy waves for diamond exploration.

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Seismic Surveys

Maps underground rock structure with sound waves in diamond exploration.

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Indicator Minerals

Minerals found near diamond deposits, signalling their presence.

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Geochemical Testing

Analyzes samples for elements present in Indicator minerals for diamond exploration.

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Microdiamond Testing

Finds diamonds in drill cores or secondary deposits for viability assessment.

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Character Sampling

Analysis of diamond size, shape, clarity, and color after processing a large amount of material.

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Ore Grade

Concentration of diamonds in 100 tons of rock, measuring diamond richness.

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Primary Diamond Deposits

Diamonds found within the kimberlite or lamproite pipes of origin.

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Secondary Diamond Deposits

Diamond deposits outside the kimberlite pipes, often in river sediments.

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Carbonado

A very hard diamond made of interlocking tiny diamond crystals.

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Diamond Formation Rocks

Diamonds primarily form in peridotite and eclogite rocks.

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Carbonate

A class of chemical compounds containing carbon and oxygen.

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CLIPPIR Diamonds

Diamonds with specific characteristics: Cullinan-like, large, inclusion-poor, pure, irregular, and resorbed.

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Diamond Formation Conditions

High pressure and temperature, plus a carbon source, are needed for diamond formation.

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Core (Earth)

The innermost layer of the Earth.

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Mantle Keels & Cratons

Diamond-forming conditions are found in mantle keels beneath cratons.

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Types of Mined Diamonds

Most mined diamonds are lithospheric or superdeep, originating from different depths within the Earth's mantle.

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Cratons

Large, ancient, stable parts of the Earth's continental landmasses.

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Superdeep Diamonds

Form much deeper within the Earth's mantle than other diamonds.

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Crust (Earth)

The Earth's outermost layer.

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Crustal Diamond

Diamonds formed in the continental crust due to meteorite impact or tectonic plate collision.

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Carbon Availability

Diamonds form in mantle keels when carbon is free to bond without oxygen.

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Eruption (Geological)

A geological process that brings material to the surface.

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Diamond Formation Clues

Inclusions within a diamond can indicate where it formed within Earth.

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Geothermal Gradient

The rate of temperature increase with depth in the Earth.

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CLIPPIR Diamonds

Diamonds that crystallize from metallic melts in the Earth's mantle's transition zone or lower mantle.

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Igneous Rock

Rock formed from molten material.

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Blue Diamond Color

Boron is the most common cause of blue color in diamonds.

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Lithosphere

The layer containing the crust and uppermost mantle.

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Boron Origin

Boron in blue diamonds comes from oceanic plates.

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Carbonado Diamond

The hardest form of diamond.

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Magma

Molten rock within the Earth.

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Diamond Surface Delivery

Diamonds reached the Earth's surface between 2.5 billion and 20 million years ago.

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Mantle (Earth)

The layer between the Earth's crust and core.

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Diamond Transportation Rocks

Kimberlite and lamproite rocks transport diamonds to the surface.

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Mantle Keels

Large, downward-protruding portions of the lithosphere under a craton.

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Kimberlite vs Lamproite

Kimberlite is much more common than lamproite for diamond-bearing deposits, and typically found in craton centers compared to lamproite found at the edges.

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Metamorphic Rock

Rock changed by heat and pressure.

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Metasomatism

Chemical changes in rocks from external sources.

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Pipe Deposits

Kimberlite and lamproite form pipe-shaped deposits.

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Economic Diamond Deposits

Few kimberlites or lamproites contain diamond economically.

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Mineral

A natural, inorganic substance with a specific chemical composition and structure.

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Pipe (Geological)

A deep, vertical geological formation.

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Plate Tectonics

The study of Earth's moving plates.

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Rocks

Material made of one or more minerals.

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Subduction

One plate sliding under another.

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Superdeep Diamonds

Diamonds formed at depths of 410 km or more.

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Transition Zone (Earth)

Layer between the upper and lower mantles.

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Study Notes

Diamond Exploration & Mining

  • Primary Deposits: Diamonds found in kimberlite or lamproite pipes that brought them to the surface.
  • Secondary Deposits: Diamonds found outside pipes, often in alluvial (river) or marine deposits. Secondary deposits are typically richer in higher-quality diamonds due to erosion.
  • Diamond Exploration Process: Takes over 10 years, beginning with searching for deposits and culminating in mining. Clifford's rule notes that kimberlites occur on cratons. Scientists now look at areas around cratons, too. Sound waves were initially used to locate diamond deposits based on how density affects wave speed. This was superseded by other methods like gravity surveys (variations in ground density to locate pipes), magnetic & electromagnetic surveys (sending/detecting energy waves to map underground rock formations) and seismic surveys (similar to magnetic and electromagnetic surveys, but using sound waves).
  • Locating Deposits: Indicator minerals like garnet, spinel, diopside, olivine, ilmenite, chromite, & perovskite can signal nearby kimberlite or lamproite pipes. Geochemical testing of rock, soil or vegetation is also used, for example examining chemical composition.
  • Testing Deposit Viability: Samples are taken to test for the presence and type of diamonds, size, shape, clarity and color. Microdiamond testing analyzes cores from primary deposits or from sediments for secondary deposits. Character sampling assesses 500 tons of earth to determine ore grade (diamond concentration per 100 tons of rock). Bulk sampling of 5,000-10,000 tons is used for accurate evaluation.
  • Primary Deposit Mining: Digging out materials around the pipe to get the diamonds.
  • Open Pit Mining: Removing overburden (rock/soil) above the pipe, blasting the ore, and then excavating the remaining material.
  • Underground Mining: Tunneling into and around the pipe to access the ore. Drifts are drilled to extract ore.
  • Diamond Recovery: Ore is reduced in size for easier processing. Dense media separation is used to separate diamond-bearing ore from lighter waste materials. Grease belt and X-ray separation are other recovery methods that rely on different properties of diamonds vs the other minerals mixed in with the ore.

Major Diamond Sources

  • Africa: Major producers, including Botswana with the Orapa and Jwaneng mines and Russia.
  • Australia: Had major diamond production (Argyle), but production drastically decreased starting in 2020.
  • Americas: Canada is an important producer with the Ekati and Diavik mines. The US has low economic significance in diamond mining.
  • Eurasia: India was once a main producer, but Russia has taken a lead role.

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Description

This quiz covers the key aspects of diamond exploration and mining, including primary and secondary deposits. It details the exploration process, methods for locating diamond deposits, and insights into the geological formations involved. Test your knowledge on diamond mining techniques and terminology.

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