Chapter 4 Key Concepts & Terms Flashcards
What type of deposits do most diamonds mined today come from?
Primary deposits
Which type of deposits contain a higher percentage of gem-quality diamonds?
Secondary deposits
Where do geologists focus their search for primary diamond deposits?
Cratons
In which locations do geologists look for secondary diamond deposits?
Rivers, streams, and estuaries flowing away from cratons
What do various surveys help geologists do in diamond exploration?
Narrow the search areas for diamonds
What is required to assess potential diamond content in secondary deposits?
More bulk sampling
What mining method removes diamond-bearing ore from a large opening at the surface?
Open-pit mining
What is the most common method of underground diamond mining?
Cave mining
What are the three main steps of diamond recovery?
- Sizing
- Concentrating
- Recovering
How is sizing accomplished in diamond recovery?
Through a series of crushing and scrubbing
What caused a shift in emphasis from secondary to primary diamond mining?
Improved technology
Where is the largest known marine diamond deposit in the world located?
Namibia
How many main regions produce the majority of diamonds today?
Four main regions
Which continent is home to the world’s most diverse diamond sources?
Africa
Which country is a top diamond producer in terms of both value and volume?
Botswana
Which mine in Australia was once a major colored diamond producer?
Argyle mine
What is Canada’s rank as a diamond producer in terms of value and volume?
Third-largest
From what type of deposits are Brazil’s diamonds predominantly mined?
Alluvial deposits
What percentage of the world’s rough diamond supply does Russia provide?
About a third
What are 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.
Define bulk sampling.
Large-scale character sampling of 5,000 to 10,000 tons of rock.
What is cave mining?
An underground mining technique in which orebody is drilled beneath the surface, loosened, and collected as it falls.
What does character sampling test?
The size, shape, clarity, and color of the diamonds in a deposit based on 500 tons of rock.
What is dense media separation?
A recovery process that separates diamonds from lighter materials.
Define drift in mining.
A horizontal tunnel drilled through a diamond pipe.
What is geochemical testing?
An analysis that determines the chemical composition of a sample.
What is a grease belt?
A mechanism that uses diamond’s affinity for grease to separate diamonds from other minerals.
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.
Define marine deposit.
A secondary diamond deposit created by rivers or streams carrying diamonds to the shoreline or ocean floor.
What is microdiamond testing?
Screening for the presence of tiny diamonds in a sample.
What does ore grade measure?
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.
Define parcel in diamond mining.
A quantity of stones, sometimes of similar size and quality, packaged together for sale or storage.
What is a primary deposit?
A deposit where gems are found in the rock that carried them to the surface.
Define recovery in the context of diamonds.
A process used to separate diamonds from host rock or sediments.
What is a secondary deposit?
A deposit where gems are found away from their primary source.
What is a shaft in mining?
A vertical tunnel drilled in stable rock near the pipe to provide access for personnel, equipment, supplies, and ventilation.
What is sizing in diamond processing?
A process used to reduce diamond-bearing ore to smaller, more manageable sizes.
What does X-ray separation utilize?
A recovery method that uses X-rays to detect diamonds and an air jet to remove them from the ore.
