Ass #4 - Key Terms & Concepts PDF

ASS #4 : Key Terms Alluvial Deposit—A deposit where gems are eroded from their source rock and then transported away from the source and further concentrated in rivers and streams. Bulk Sampling—Large-scale character sampling of 5,000 to 10,000 tons of rock. Cave Mining—An underground m...

ASS #4 : Key Terms Alluvial Deposit—A deposit where gems are eroded from their source rock and then transported away from the source and further concentrated in rivers and streams. Bulk Sampling—Large-scale character sampling of 5,000 to 10,000 tons of rock. Cave Mining—An underground mining technique in which orebody is drilled beneath the surface, loosened, and collected as it falls. Character Sampling—Testing the size, shape, clarity, and color of the diamonds in a deposit based on 500 tons of rock. Dense Media Separation—A recovery process that separates diamonds from lighter materials. Drift—A horizontal tunnel drilled through a diamond pipe. Geochemical Testing—An analysis that determines the chemical composition of a sample. Grease Belt—A mechanism that uses diamond’s affinity for grease to separate diamonds from other minerals. Indicator Minerals—Minerals that form along with diamonds at great depths and are brought to the surface by the same kimberlite or lamproite. Marine Deposit—A secondary diamond deposit created by rivers or streams carrying diamonds to the shoreline or ocean floor. Microdiamond Testing—Screening for the presence of tiny diamonds in a sample. Ore Grade—The concentration of diamonds in a deposit, measured by the amount of diamonds in 100 tons of earth removed. Overburden—Rock or soil that covers a diamond-bearing orebody. Parcel—A quantity of stones, sometimes of similar size and quality, packaged together for sale or storage. Primary Deposit—A deposit where gems are found in the rock that carried them to the surface. Recovery—A process used to separate diamonds from host rock or sediments. Secondary Deposit—A deposit where gems are found away from their primary source. Shaft—A vertical tunnel drilled in stable rock near the pipe to provide access for personnel, equipment, supplies, and ventilation. Sizing—A process used to reduce diamond-bearing ore to smaller, more manageable sizes. X-Ray Separation—A recovery method that uses X-rays to detect diamonds and an air jet to remove them from the ore. Key Concepts : Most diamonds mined today come from primary deposits. Diamonds are more concentrated in secondary deposits than in primary deposits. Secondary deposits contain a higher percentage of gem-quality diamonds than primary deposits. Geologists focus the search for primary diamond deposits on cratons. Geologists look for secondary diamond deposits in rivers, streams, and estuaries flowing away from cratons. Various surveys help geologists further narrow the search areas for diamonds. Secondary deposits require more bulk sampling than primary deposits to assess potential diamond content. Open-pit mining removes diamond-bearing ore from a large opening dug at the surface of the earth. Cave mining is the most common method of underground diamond mining. Key Concepts continued....... The three main steps of diamond recovery are sizing, concentrating, and recovering. Sizing is accomplished through a series of crushing and scrubbing. Improved technology caused a shift in emphasis from secondary to primary diamond mining. The largest known marine diamond deposit in the world is in Namibia. Today the majority of diamonds are produced in four main regions. Africa is home to the world’s most diverse diamond sources. Botswana is a top diamond producer in terms of both value and volume. Australia’s Argyle mine was once a major colored diamond producer. Canada is the third-largest diamond producer in terms of both value and volume. Brazil’s diamonds are mined predominantly from alluvial deposits. Russia provides about a third of the world’s rough diamond supply.