X-Ray powder diffraction (XRD) is a technique that is used to quantify and identify undetermined crystalline materials that are present in a sample being tested. Basically, each crystalline substance has a unique diffraction pattern that can be discovered via the XRD process. By comparing the pattern against available reference databases, the scientist or technician can determine exactly which minerals are present.
In addition to identifying the specific crystalline material, the X-Ray diffraction technique can be used to provide information about the structure of the crystal and its phases and orientation. The average size of the grains and their percent of crystallinity can also be determined. If you are testing a sample of mixed elements, XRD can be used to identify the percentage of each of the minerals. You can also use the technology to uncover deviations from ideal mineral composition.
Key XRD Applications
XRD is used across many fields, ranging from pharmaceuticals and biology to geology and environmental sciences to help identify both inorganic compounds and the mineral components of a sample. One of the uses is to help quantify and specify the exact composition of mixed layers or fine clays that cannot be easily identified optically. You can also use X-Ray diffraction to reveal specific unit cell measurements and to examine the purity of a sample.
The Origin and Formation of Ore Minerals
When minerals are formed, they do so under very specific bands or ranges of pressure and temperature. X-Ray diffraction can be used to help determine likely conditions during formation of the ore and subsequent geologic factors that caused the original ore to be altered.
Stratigraphic Studies and Analysis of Coal Beds
Using XRD it was possible to do stratigraphic studies of buried soil horizons from ancient times, also called paleosols. By studying the paleosols in conjunction with the underclay typically found beneath coal beds, it was possible to identify prominent Appalachian basin coal zones. These in turn were correlated with coal deposits in the Western Interior region.
Discovering Minable Coal Formations
When geologists are searching for minable coal formations, they can use X-Ray diffraction to do an evaluation of both the vertical and lateral differences of minerals in the coal bed. XRD allows the identification of the mix of major, minor and other trace minerals in the formation. By analyzing all of this data, it’s possible to develop an understanding of the potential and viability of minable deposits.
Combining XRD and Remote Sensing Data
With Cascade range volcanoes there is a dangerous possibility of large landslides and potential mudflows. In order to quantify and evaluate the risks, geologists have developed innovative studies that combine X-Ray diffraction with data from remote sensing. Specifically, XRD is used to help determine which minerals are present in the rocks in the area being surveyed. These rocks, which have typically been altered by hydrothermal affects and are rich in clay, are understood to be a significant factor in generating mudflows and slides.
When you are interested in determining the specific minerals and crystallogy of a test sample, X-Ray powder diffraction is an effective choice. It can also be combined with other testing technologies, such as remote sensing, to give a comprehensive picture of the risks associated with geologic formations in the regions being studied.
