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Gazzi-Dickinson method
The Gazzi-Dickinson method is a point-counting technique used in geology to statistically measure the components of a sedimentary rock, chiefly sandstone. The main focus (and most controversial) part of the technique is counting all sand-sized components as separate grains, regardless of what they are connected to. Gazzi-Dickinson point counting is used in the creation of ternary diagrams, such as QFL diagrams.
==Technique==
To perform a point count using the Gazzi-Dickinson method, a randomly selected thin section from a sedimentary rock is needed, with a slide advance mechanism that will randomly select points on the slide with a petrographic microscope. A minimum of 300 representative points (preferably 500 points) should be used to perform the count. On each randomly selected point that lands on a sand grain, the operator must determine the make-up of the area chosen, i.e. whether it is a mineral grain that is sand sized (larger than 62.5 micrometers) or a finer-grained fragment of another rock type, called a lithic fragment (e.g. a sand-sized piece of shale). These counts are then converted to percentages and used for compositional comparisons in provenance studies. Typically, only framework (non-matrix) grains are counted, or non-framework grains are counted and then excluded from percentages when using descriptive devices such as QFL triangles. This can create problems with pseudomatrix, which are lithic grains that have been deformed and thus blend in with (or have become) matrix.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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