Development of USGS Geochemical Reference Materials

Science Center Objects

The project focus was the development of traditional and microanalytical reference materials that support USGS geochemical investigations. Development of new microanalytical reference materials allows USGS scientists and outside customers to examine a greater range of sample types while maintaining a high degree of data reliability.

Reference Material Certificates | Science Issue & Relevance | Activities | Collaborations | Impact

USGS Geological Reference Material Certificates


The Geologic Reference Materials (GRM) project chief retired from the USGS in January 2021. The project is currently under review for funding and structure. Distribution of existing GRMs is currently suspended while documentation is updated to meet the latest internal quality assurance standards and supplies are inventoried. There will be gradual roll out of available GRMs as documentation is approved and inventories are solidified. This website will be updated as GRMs become available and will provide information on how to order the available materials.


Science Issue and Relevance

Development of our nation's mineral resources depends on finding new deposits, evaluating the scale of new and existing resources, and developing extractive procedures that can remove the desired resource from its host rock in an economical manner. Geochemistry plays an important role in all stages of this process.

Most of this nation’s surficial mineral deposits have already been found and exploited, so geologists need to hunt for clues that indicate the presence of resources hidden underground. The geochemical analysis of rock outcrops, soils, and stream sediments can point to areas favorable for the discovery of new mineral resources. This exploration effort is typically followed by drilling programs that pinpoint the location and size of a deposit. Critical to all of this work is the reliable chemical/mineralogical analysis of collected samples. The availability of well characterized geochemical reference materials is an important part of any analysis program. Having reference materials that are similar in composition to the unknown samples provides the highest degree of reliability.

Unconventional petroleum resource development has boomed in the U.S. over the last 10-15 years, primarily from the Bakken Formation in the northern Great Plains and the Eagle Ford Shale in southern Texas. The chemistry and mineralogy of these black shales are key parameters in the decision-making process affecting horizontal drilling and hydraulic fracturing operations. However, the wide diversity of formation age, mineralogy, chemistry, organic matter, and water content makes development of comprehensive or unified models difficult. The development of black shale geochemical reference materials may assist in exploration related decision-making.

Current Activities

scientist collecting material in field

USGS scientist Stephen Wilson collecting granodiorite samples in Colorado to create a geologic reference material.

(Public domain.)

Continued development of geologic reference materials for rare earth element (REE) analysis: goal is to produce a series a REE reference materials from a variety of matrix types.

Development of field portable instrumentation for geochemical analysis: Evaluate USGS field portable Energy Dispersive X-ray Fluorescence (pEDXRF) and Laser Induced Breakdown Spectrometer (LIBS) instruments in terms of which elements are best done by the respective technique. 

Development of new and replacement USGS geologic reference materials: A need exists for a series of mineralogical-based references materials designed to support X-ray diffraction (XRD) analysis. Additionally, dwindling supplies of traditional USGS reference materials require the creation of replacement materials from either the original sources, if possible, or a suitably similar source material.

Development of microanalytical reference materials: The expanding use of microanalytical analysis has created a continual need for new microanalytical reference materials.

External Collaborations

The USGS in collaboration with industry partners is developing a series of geochemical reference materials in support of the shale gas and rare earth element industries. Materials have been collected and information about these forthcoming new materials has been presented at selected industry conferences.

Complete characterization of new black shale reference materials: The shale gas reference materials are designed to assist the industry in identifying optimal drilling zones in subsurface shale gas formations. Materials collected from outcrops associated with the five major domestic shale gas formations will be transformed into geochemical reference materials which will be characterized for their mineralogical and elemental composition. These matrix-matched reference materials will provide for a more accurate calibration of instruments, thereby improving the reliability of data needed to address a wide range of analytical quality control issues challenging the petroleum industry. 

Phosphate Rare Earth Element Reference Materials: Efforts in the area of rare earth element resource development are focused on Arkansas phosphate formations. USGS studies have identified selected domestic phosphate deposits as potential rare earth element resources. Rare earth elements are used in a variety of military and commercial products that are integral parts of our economy. With our current reliance on China for most rare earth element supplies, it is important to determine if domestic resources can supply future demand. Development of Arkansas phosphate reference materials will have two purposes. The first will be to develop instrument calibration materials designed to instantaneously provide laboratory quality analyses in the field. The second will focus on development of extraction procedures that optimize the extraction of rare earth elements while producing a phosphate product that could be integrated into the phosphate industry supply stream. The ability to produce two important products while minimizing waste is an important aspect of this work.

Technological advances in emerging defense and energy-related technologies are critically dependent on the availability of reliable supplies of heavy rare earth elements. Currently, more than 95% of the world’s supply of these is produced in China, but a potential domestic source of heavy rare earth elements has been identified in the Love Hollow phosphate deposit of north-central Arkansas. We will develop a set of geochemical standards specific to this deposit that will characterize its mineralogy and heavy rare earth element content. These standards can be used to calibrate instrumentation used for assaying additional samples from Love Hollow to determine its overall heavy rare earth element content. Another avenue of research is the development of new technologies that will merge commercial phosphate production and an economic extraction of heavy rare earth elements from their phosphate host material.

Potential Impact

Proper use of shale gas reference materials will allow the energy sector to efficiently identify optimal horizontal drill zones for fracking which can lower development costs and increase well production. The materials will also assist in the identification of new shale gas formation around the world which may have substantial impact on domestic and international energy markets.

Exploitation of phosphate ore deposits could play a major role in increasing available rare earth element resources internationally. Optimizing rare earth element and phosphate extraction procedures using the Arkansas phosphate ore would be a first step in evaluating if these resources can be efficiently developed. Given the estimated domestic phosphate resources and the ease with which rare earth elements can be extracted this resource could have a positive impact on the availability of these technologically important elements.


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