Attachment H_USGS_EMRI_Protocols_sir20255068.pdf

PDF 2 MB Posted Mar 27, 2026

Attached to: Earth Mapping Resources Initiative (Earth MRI) Mine Waste Cooperative Agreements FY2026
Opportunity number: G26AS00102
Issued by: Department of the Interior US Geological Survey

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Written by GovTribe AI · Mar 28, 2026

This is a scientific protocols document published by the U.S. Geological Survey (USGS) Earth Mapping Resources Initiative (Earth MRI) establishing standardized methods for sampling hard-rock mine waste and perpetual mine water sources. The document was created to support evaluation of critical mineral resources in aboveground mine waste across the United States by participating State geological surveys and their cooperators.

The protocols establish comprehensive field sampling procedures for solid mine waste materials including tailings, waste rock, gangue, heap leach piles, ore stockpiles, slag, and other mineralized processed materials. For solid sampling, the document specifies minimum requirements of 30 subsample locations per sample unit with equal volumes combined into composite samples of at least 1 kilogram dry weight, with separate methodologies provided for fine-grained materials (less than 2 millimeters), mixed particle size materials, large cobble-to-boulder materials (greater than 30 centimeters), and drill core samples. For water sampling from pit lakes and draining adits, protocols specify collection of five bottle splits for metals and cations (raw and filtered), precious metals (filtered), anions (filtered), and alkalinity or acidity (filtered), with specific preservation requirements including acid preservation with nitric acid and chilling on ice. Field parameters to be measured include pH, temperature, specific conductance, and optionally dissolved oxygen and oxidation-reduction potential. Samples are submitted to the USGS Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, with solid samples analyzed for metals via ICP-MS and ICP-OES (61 elements), mineralogy via X-ray diffractometry, acid-base accounting, and major element oxides via X-ray fluorescence, while water samples are analyzed for metals, anions, and alkalinity or acidity, with all data publicly released through ScienceBase.

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Attachment H_USGS_EMRI_Protocols_sir20255068.pdf

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File	Type	Posted
Mod 1 2026 EMRI Mine Waste NOFO.docx	DOCX document	Mar 31, 2026
Attachment Figures 1 and 2.pdf	PDF	Mar 27, 2026
Attachment G - Current and Pending Common Form.pdf	PDF	Mar 27, 2026
Attachment F - Biographical Sketch Form.pdf	PDF	Mar 27, 2026
Attachment E_DroneGuidance.pdf	PDF	Mar 27, 2026
Attachment D - EMRI Mine Waste Terms & Conditions.pdf	PDF	Mar 27, 2026
Attachment C_DMP.pdf	PDF	Mar 27, 2026
Attachment B_budget_sheets.pdf	PDF	Mar 27, 2026
Attachment A_summary.pdf	PDF	Mar 27, 2026
Final 2026 EMRI Mine Waste NOFO G26AS00102.pdf	PDF	Mar 27, 2026

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U.S. Department of the Interior U.S. Geological Survey

Scientific Investigations Report 2025–5068

Mineral Resources Program

Earth Mapping Resources Initiative Protocols—Sampling Hard-Rock Mine Waste and Perpetual Mine Water Sources

Cover. A Colorado Geological Survey staff member uses the Earth Mapping Resources Initiative mine waste sampling protocols to collect a composite sample at the Montezuma Mine, Colorado (Photograph by Kate Campbell, U.S. Geological Survey).

Earth Mapping Resources Initiative Protocols—Sampling Hard-Rock Mine Waste and Perpetual Mine Water Sources

By Kate M. Campbell, Robert R. Seal, Nadine M. Piatak, Jaime S. Azain, Jean M.

Morrison, Sarah Jane White, Andrew H. Manning, Katherine Walton-Day, JoAnn M. Holloway, and Bronwen Wang

Mineral Resources Program

Scientific Investigations Report 2025–5068

U.S. Department of the Interior U.S. Geological Survey

U.S. Geological Survey, Reston, Virginia: 2025

For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment—visit https://www.usgs.gov or call 1–888–392–8545.

For an overview of USGS information products, including maps, imagery, and publications, visit https://store.usgs.gov/ or contact the store at 1–888–275–8747.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Campbell, K.M., Seal, R.R., Piatak, N.M., Azain, J.S., Morrison, J.M., White, S.J., Manning, A.H., Walton-Day, K., Holloway, J.M., and Wang, B., 2025, Earth Mapping Resources Initiative protocols—Sampling hard-rock mine waste and perpetual mine water sources: U.S. Geological Survey Scientific Investigations Report 2025–5068, 22 p., https://doi.org/10.3133/sir20255068.

ISSN 2328-0328 (online) https://www.usgs.gov/survey-manual/11006-use-copyrighted-material-usgs-information-products https://doi.org/10.3133/sir20255068 iii

Acknowledgments

The authors acknowledge the invaluable input by Virginia McLemore (New Mexico Bureau of Geology and Mineral Resources), Michael O’Keefe (Colorado Geological Survey), James Ranville and Aaron Goodman (Colorado School of Mines), Gary D. Fowler III, Benjamin L. Davis, and Mary Lupo (Florida Geological Survey). The authors appreciate reviews provided by Tanya Gallegos (U.S. Geological Survey [USGS]) and Mojisola KunleDare (USGS), and the support of the USGS Mineral Resources Program and Earth Mapping Resources Initiative, including Warren Day, Darcy McPhee, Jamey Jones, Colin Williams, Patricia Loferski, and James Mosley.

Contents Acknowledgments��iii Abstract��1 Introduction��1 Purpose and Scope��2 Protocols for Sampling Solids��2

Defining Sample Units, Locations of Subsamples, and Depths of Subsamples��2 Grab Samples��3 Protocols for Composite Sample Collection of Several Mine Waste Material Types��3

Tailings and Fine-Grained Waste Material��3 Personal Protective Equipment��3 Equipment��4 Subsample Depth and Amount Collected��4 Compositing Subsamples and Sieving��4

Material Containing a Mix of Small and Large Particles��5 Personal Protective Equipment��5 Equipment��5 Subsample Depth and Amount Collected��5 Compositing Subsamples, Sieving, and Processing Greater Than 2

Millimeter Fraction��5 Large Material Predominantly Greater Than 30 Centimeters��6

Personal Protective Equipment��6 Equipment��6 Subsampling Approach��6

Drill Cores��7 Equipment��7 Determining Sample Intervals (Sample Units) Within a Core��7 Collecting Composite Samples��7

Duplicates and Blanks for All Solid Sample Types��7 Equipment Cleaning in Between Sample Units��8 Sample Labeling, Handling, and Storage for All Sample Types��8 Extra Equipment for Sampling Solids��8

Protocols for Water Sample Collection, Preservation, Measurement of Field Parameters and Flow��9

Equipment and Preparation��9 Personal Protective Equipment��9 Bottle Sets��10 Acid Washing Bottles for Cation and Metal Sample Splits��10 Deionized Water Rinse for Anion and Alkalinity or Acidity Sample Bottles��10 Cleaning Pumps and Tubing��11 Filters��11 Water Collection Containers��11 Preservation Reagents and Distribution Equipment��11 Water for Blanks��12 Extra Equipment for Water Sampling��12 vi

Equipment Reuse��12 Field Parameters��12

Water Collection Protocol��13 Rinsing with Sample��13 Filtration��13 Preservation of Water Samples��13 Quality Assurance and Quality Control—Duplicates and Blanks��13 Sample Handling, Storage, and Shipping��13

Flow and Discharge Measurements��13 Load Calculations��14 Field Parameters��14 pH��14 Specific Conductance��14 Temperature��15 Oxidation-Reduction Potential��15 Dissolved Oxygen��16

Field Sheet, Notes, and Observations��16 Additional Suggested Observations��17

Collecting Geospatial Data��17 Tailings—Composite Sample Sites��17 Water—Sampling Locations��17 Site and Feature Boundaries—Polygons��17 Volume Estimates of Tailings and Other Mine Waste Piles��17 Volumes of Flowing Adits and Pit Lakes��17

Sample Submission and Geochemical Analyses��18 Sample Submission��18 Solid Phase Analyses��18

Metals and Other Elemental Analyses��18 Mineralogy��19 Acid-Base Accounting��19 Quality Assurance and Quality Control��19

Aqueous Analyses��19 Quality Assurance and Quality Control��19

Sample Archive��19 Data Reporting��19

Summary��19 References Cited��20 Appendix 1. Example Field Sheets��22

Figures

1. An example sample label for solid composite samples��8

2. Conceptual flow chart of water sample collection and preservation��9

3. Example labels for a hypothetical water sample split of metals and cations��11

vii

Tables

1. Overview of bottles, preparation, and preservation for water samples��10

Conversion Factors International System of Units to U.S. customary units

Multiply By To obtain

Length centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) meter (m) 1.094 yard (yd) kilometer (km) 0.6214 mile (mi) micrometer (μm) 0.00003937 inch (in.)

Area square kilometer (km2) 247.1 acre square kilometer (km2) 0.3861 square mile (mi2)

Volume liter (L) 0.2642 gallon (gal) Mass gram (g) 0.03527 ounce, avoirdupois (oz) kilogram (kg) 2.205 pound avoirdupois (lb)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F = (1.8 × °C) + 32.

Supplemental Information Specific conductance is given in microSiemens per centimeter (μS/cm).

Oxidation-reduction potential (ORP) is given in millivolts (mV).

Volumes are given primarily in milliliters (mL).

Dissolved oxygen is given in milligrams per liter (mg/L).

viii

Abbreviations ~ about

-FA filtered, acidified

-FALK filtered, alkalinity

-FU filtered, unacidified

-RA raw, acidified

AP acid generating potential

BPL Big Pit Lake

DI deionized

DO dissolved oxygen

Earth MRI Earth Mapping Resources Initiative

ETS Example Tailings Site

GIS geographic information system

GPS global positioning system

ICP–MS inductively coupled plasma mass spectrometry

ICP–OES inductively coupled plasma optical emission spectroscopy

ID identification

NP neutralization potential

NNP net neutralization potential

ORP oxidation-reduction potential

PPE personal protective equipment

QA/QC quality assurance and quality control

SC specific conductance

T temperature

USDA U.S. Department of Agriculture

USGS U.S. Geological Survey

Earth Mapping Resources Initiative Protocols— Sampling Hard-Rock Mine Waste and Perpetual Mine Water Sources

By Kate M. Campbell, Robert R. Seal, Nadine M. Piatak, Jaime S. Azain, Jean M. Morrison, Sarah Jane White, Andrew H. Manning, Katherine Walton-Day, JoAnn M. Holloway, and Bronwen Wang

Abstract Supporting the overarching goal to evaluate critical minerals nationwide, the mine waste characterization effort in the U.S. Geological Survey (USGS) Earth Mapping Resources Initiative has created a series of protocols to standardize sampling carried out under this effort by the participating State geological surveys and their cooperators. The protocols are based on published, reviewed methods that can be deployed in the field. The protocols include (1) collecting and processing composite samples of mine and mill waste, including tailings, waste rock, gangue, heap leach piles, ore stockpiles, slag, or other mineralized and processed materials and (2) collecting and preserving water samples from perpetual or long-term mine water sources. The protocols also specify information to document on field sheets and detail the collection of geospatial data. The analytical methods used by the USGS and USGS contract laboratories are described in this report, including the data delivery pathway for USGS-derived data.

Introduction The U.S. Geological Survey (USGS) Earth Mapping

Resources Initiative (Earth MRI) is an effort to modernize mapping of the Earth’s surface and subsurface across multiple types of data, including geologic, geophysical, geochemical, and topographical data (https://www.usgs.gov/earth-mapping-resources-initiative-earth-mri). Critical minerals are materials essential to the economic and national security of the United States with possible vulnerability to supply chain disruption (Nassar and others, 2020). Areas across the United States with the potential to host subsurface and surface deposits of critical mineral resources (“focus areas”) were identified by the USGS and their State geological survey collaborators (Hammarstrom and others, 2023). Earth MRI focus areas are based on mineral systems, deposit types, and known and potential critical mineral commodities. The mineral systems classification links large mineral systems that may contain multiple deposit types to the mineral commodities associated with each deposit type (Hofstra and Kreiner, 2020). Earth MRI takes a mineral systems approach for prioritizing data collection efforts for aboveground and belowground critical mineral resources. One aspect of Earth MRI is to understand the distribution of critical minerals in aboveground mine waste.

The Earth MRI mine waste characterization effort collects compositional data to help identify mine waste sites that potentially contain critical mineral resources. The data can be used to estimate the critical mineral endowment of mine waste in the United States. Additionally, the data can be used to identify potential mineral hosts of critical minerals and provide a cursory evaluation of the environmental characteristics of the mine waste to help delineate potential reprocessing, environmental management, reclamation strategies, and other attendant costs. Identification of sites with critical mineral potential is the first step toward fostering economic development in conjunction with environmental remediation. Whether mine waste is a potential resource, an environmental liability, or both will depend on the geochemical and mineralogical characteristics of the waste.

In addition, compositional characterization of mine waste may inform the use of new technologies to reprocess mine waste more efficiently for the extraction of critical minerals in the future. This information will be useful when assessing the total costs and benefits of reuse, recycling, reprocessing, reclamation, and restoration of ecosystem services. Evaluation of the future recoverability of critical minerals from mine waste is beyond the scope of this report and will depend on a variety of factors, including prevailing commodity prices, technological innovations, and financial incentives.

The goal of Earth MRI mine waste characterization effort is to develop a comprehensive and internally consistent national database of mine waste locations, volume and mass estimates, bulk geochemical composition, bulk mineralogical composition, and contained mineral commodities. To this end, this report describes the methods followed by participating State geological surveys and their cooperators to standardize sampling carried out by Earth MRI’s mine waste characterization effort.

https://www.usgs.gov/earth-mapping-resources-initiative-earth-mri https://www.usgs.gov/earth-mapping-resources-initiative-earth-mri

2 Earth Mapping Resources Initiative Protocols

Purpose and Scope This report is intended to supplement inperson guidance that the USGS provides to participating State geological surveys. The scope of these protocols encompasses sampling of solid mine waste and large perpetual mine-related water sources (for example, pit lakes and draining adits). This report presents an approach to sampling a variety of solid waste types, including tailings, waste rock, gangue, heap leach piles, ore stockpiles, slag, or other mineralized and processed materials. If other types of materials are present at a site (for example, efflorescent salts, secondary precipitates, or streambed sediments) and the opportunity to sample is available during the course of a study, consult with USGS Earth MRI personnel on methodologies for sampling. Optional field sheets that provide guidance on general field notes and geospatial data are provided in appendix 1.

Many mine waste sites may be vertically heterogeneous.

Vertical profile sampling, in addition to composited surface samples, may be considered. These protocols include an approach to sampling drill core; methodologies for drilling, trench sampling, or other vertical sampling techniques are not discussed in detail in this report because they are highly site dependent.

Safety planning, including job hazard analysis, selection of personal protective equipment (PPE), and appropriate safety training, is the responsibility of the State agency conducting the work. The USGS is not responsible for providing equipment, safety training, or evaluating site hazards and risks. Work with the responsible organization’s safety officer to determine and complete the necessary safety requirements to perform the proposed work in a safe manner. Required PPE is provided as a guide for sample collection requirements.

Additional PPE may be needed to conduct the work safely.

Protocols for Sampling Solids Sampling of solid mine waste is complex because of the varied nature of source material, waste management approaches, meteorological effects, and site accessibility.

Sampling described in these protocols are primarily focused on surficial material (0–10 centimeter [cm] depth; exceptions are described in the “Defining Sample Units, Locations of Subsamples, and Depths of Subsamples” section) using a statistically based, relatively rapid, composite sampling approach based on Smith and others (2000) and Naftz and Walton-Day (2016). Before sampling, divide the site into appropriate sample units as described in detail in the “Defining Sample Units, Locations of Subsamples, and Depths of Subsamples” section. Within each sample unit, the area is subdivided into a grid or randomized distribution of at least 30 subsample locations. For statistical rigor, a minimum of 30 subsample locations is required; more than 30 subsamples are acceptable. After collecting subsamples of equal volume and combining them into a single composite sample that has a minimum combined dry weight of 1 kilogram (kg), the sample is sent to USGS Sample Control, where it will be crushed and homogenized prior to submission for analysis.

Defining Sample Units, Locations of Subsamples, and Depths of Subsamples

The overall objective of designating sample units is to differentiate parts of a site that potentially could have different material composition or to divide a very large area into smaller units to obtain a series of composite samples that are more representative of a site. The number of sample units will depend upon the size, topography, mine waste type, ore-processing history, geography of the site, and other objective criteria, such as color. For example, if the tailings pile has discrete benches, each bench may be considered as a separate sample unit. Before collecting samples at the site, it is valuable to identify the site features and boundaries using recent satellite, aerial photography, or other imagery. The features may be subdivided into sample units if the feature is large and has topographical or other distinguishing attributes that indicate a change in composition or site management (for example, benches, discrete piles, or tailings color). If the site is large with no clear distinguishing features, select sample units of approximately 0.04–0.06 square kilometers (km2).

If a pile has mixed types of waste or has areas that contain vastly different sizes of material, sample units can be drawn to reflect those differences. For example, if a pile has mixed fine-grained material and cobble-sized pieces on the top of the pile, and boulder-sized rocks with no fine material around the base of the pile, the top of the pile may be considered a separate sample unit from the base. Different sampling methods can then be used to collect composite samples in each of the two sample units.

Site history is an important tool in understanding site features. For example, locations of pipes used to convey tailings, if available, can help guide distribution patterns on the landscape. Similarly, if the site went through multiple phases of ore processing, that information may be useful in interpreting different possible stratigraphy or topographical features at a site. Aerial imagery is helpful in understanding a site but is generally not sufficient to make final decisions about sampling approach. As such, site reconnaissance can be useful to more clearly identify the geography and topography of the features and to determine if a cover has been placed over the waste material.

Once sample units have been identified, select at least 30 subsampling locations per sample unit using a systematic grid or randomized location scheme that adequately covers the sample unit. Subsample locations may be planned before field work using geographic information system (GIS) tools, and any deviations from the plan can be recorded in field notes or with a global positioning system (GPS) device. For example, if a particular preselected subsample location is inaccessible, Protocols for Sampling Solids 3 an alternative may be selected onsite as close to the original location as possible. Pin flags and flagging tape are helpful for marking out subsample locations onsite before sample collection. If subsample locations are not selected before the field work, pin flags or flagging tape can be laid out by the sampling team to visually confirm that the subsample locations adequately cover the sample unit before sampling begins, adjusting the locations and adding additional subsample locations as needed. Collect a minimum of 30 subsamples;

more than 30 subsamples is acceptable. Log the subsample locations by GPS in the field if not predetermined. If a subsample location falls on a clearly unique or different feature (for example, localized material that differs in color or texture from the surrounding tailings) within the sample unit, collect and composite it as planned (also refer to the “Grab Samples” section).

If the site has an obvious soil horizon, clay cap, engineered cover (for example, a geomembrane), or other natural or engineered covering, the sampling procedure described in the “Protocols for Composite Sample Collection of Several Mine Waste Material Types” section may need to be modified to collect the waste material below the cover as long as the sampling does not compromise the integrity of an engineered cover. Site history will be helpful in determining if an engineered cover is expected at the site. Negotiating with the landowners for sampling permission, especially if a cover is expected, is the responsibility of the State agency conducting the work. Once onsite for sampling or during a reconnaissance visit, dig a test hole, if possible, (usually approximately 0.5 meters [m] deep but the depth may vary depending on site characteristics) to visually determine if samples should be collected below the surface. For example, tailings that are not acidic may have vegetative growth and a surficial layer with roots and some soil formation. This soil layer is usually apparent in the test hole, and the sample collection depth should be below this layer for all subsamples and recorded on the field sheets. Because each site has a unique setting, contact USGS Earth MRI personnel to discuss variations in sampling design as needed.

Grab Samples

Within the sample allotment and budget, additional grab samples of any unusual or notable feature may be collected.

If the subsample location falls on a feature that is notable or different, collect and composite it as planned; additional grab samples of that feature may then be collected separately. For example, if a pile has a distinct orange weathered layer on the surface with continuous primary black unweathered tailings material below the weathered layer, collect the composite sample below the weathered surface layer; collecting a grab sample of the weathered orange surface layer at one or more subsampling locations is beneficial. If available, collect 1–2 kg of grab sample material to submit for analysis. However, if that mass is not available (for example, within a drill core or a smaller distinct layer in tailings), a smaller amount of material may be collected, and fewer chemical analyses may be completed on that sample at the discretion of the USGS.

Protocols for Composite Sample Collection of Several Mine Waste Material Types

These protocols are divided into four categories: (1) tailings and fine-grained material, (2) mixtures of small and large material, (3) predominantly large material, and

(4) drill cores. Fine-grained material is generally less than approximately 2 millimeters (mm), and is typically found in certain types of waste, such as tailings piles. It is also possible to have mine waste that is a mixture of fine material (less than [<] 2 mm) and larger material (between 2 mm and 30 cm), all of which was derived from ore processing. Other types of waste, such as waste rock, may be mainly large cobble- to boulder-sized material (greater than [>] 30 cm) with very little fine-grained material present. Sampling drill cores is a special case for recovering material from vertical drilling.

Tailings and Fine-Grained Waste Material In general, tailings are the waste material from ore that has been processed to recover a concentrated form of the target commodity. Processing usually includes some form of grinding or milling of the ore, and as a result, tailings are usually fine grained (<2 mm). For most tailings, material on the surface that is >2 mm may be the result of a cover or extraneous material deposition that should not be included in the composite sample. Sieving to <2 mm ensures that the sample collected is primarily the tailings material. Although unlikely in tailings piles, if most of the tailings have a grain size >2 mm, use the methodology described in the “Material Containing a Mix of Small and Large Particles” section or the “Large Material Predominantly Greater Than 30 Centimeters” section for larger material types. One composite sample will be collected for each sample unit, not including duplicate samples or additional grab samples.

Personal Protective Equipment

• Nitrile gloves—It is possible to cover work gloves with nitrile gloves, if desired, but work gloves alone cannot be used. Wear new nitrile gloves when sampling each sample unit to prevent cross-contamination.

• Additional PPE may be needed (for example, masks, eye protection, and clothing covering) depending on the site conditions and hazards.

4 Earth Mapping Resources Initiative Protocols

Equipment

• Shovel.

• Trowel, small shovel, or incremental sampler (using stainless steel or plastic is necessary to prevent metal contamination).

• 5-gallon plastic bucket.

• Large (1 gallon) plastic bags or other sealable containers.

• Labels and permanent markers.

• 2 mm plastic or stainless-steel sieve.

• Flagging tape and (or) pin flags to mark subsample locations. Consider the choice of color so that the flags stand out in the sampling landscape.

• Wire brush to remove particles from the sieve as needed in between samples.

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Do not use tap water because it can introduce elements that are part of the analysis package.

• Paper towels or laboratory wipes.

Rinse sampling tools, sieve, and buckets with DI water and air dry before sample collection.

Subsample Depth and Amount Collected Collect subsamples from the upper layer of the tailings pile (0–10 cm deep), unless it is necessary to sample below a soil layer, cap, oxidized layer, hardpan, or crust. Dig a test hole before the first subsample collection to determine whether there is a soil, cap, or oxidized layer on the surface of the tailings pile. Although aerial imagery and site history are helpful for guiding sampling strategy, the best way of determining if there is a layer on top of the tailings is to dig to a depth of 0.25–1 m and observe any variation in color, particle size, plant roots (if present), moisture content, and other properties. If there is an obvious soil layer or cap on top of the tailings, then collect subsamples at the same depth below the anomalous surface layer. Record evidence of weathering (often indicated by a color change or hardpan layer) on the field sheet. The inperson guidance provided by the USGS can help identify these types of situations and inform the sampling strategy on a site-by-site basis.

Collect each subsample within a sample unit to the same depth and volume using the same equipment. Ensure the mass is at least approximately 50 grams (g) per subsample. The amount collected for each subsample can be approximated using the sampling equipment, a bag, or other container, as long as the same amount of material that is collected is consistent at each subsample location. For example, if using a trowel to collect the subsample, fill the trowel with approximately the same amount of material at each location.

If using a plastic bag or container, mark the fill level with a permanent marker on the bag or container and fill to that level at each location. The method used may depend on the wetness, particle size, or other factors specific to the site material. It is not necessary to weigh each subsample. Ensure the total mass of the sieved composite sample after all the 30 or more subsamples have been combined is at least 1–2 kg dry weight.

Compositing Subsamples and Sieving Sieve composited samples to <2 mm in the field or after being transported to a laboratory setting. If possible, sieve subsamples in the field during collection. As each subsample is collected, it can be sieved directly into a bucket; each subsample is sieved and sequentially added to the same bucket, which becomes the composite sample. It is usually possible to sieve tailings materials that are damp, unless the sample has a very high clay content. The >2 mm fraction of the material will not be submitted or analyzed and can be discarded.

If the sample cannot be sieved in the field (for example, very high clay content), the bulk material from each subsample can be directly added to the bucket to be sieved later. Remove any large particles (>1 cm) and large items (>1 cm) of manufactured material (for example, bolts, screws, or rebar) in the subsample, and record large items in field notes. If the material has a large amount of coarse (>2 mm) material, additional mass may need to be collected at every subsample location to accommodate the amount of >2 mm mass discarded during sieving. If the samples have a high clay content, sieving will be challenging in the field and in the laboratory because clay can be sticky when wet and harden into large aggregates when dry. Contact USGS Earth MRI personnel for more guidance on samples with high clay content; the USGS may be able to assist with sample preparation.

If tailings samples are wet when collected, air dry the samples before submitting them to USGS sample control. If sieving is occurring in a laboratory setting after collection, disaggregate any particle agglomerates that have formed when drying before sieving. Ensure the dry weight of the sieved composite sample is at least 1–2 kg. Once the composite sample has been sieved, the material can be transferred to a plastic bag, sealed, and labeled. Double- or triple-bagging samples before shipping will prevent loss of material during transit. If more than one bag of material has been collected, it is acceptable to submit multiple bags of the same material to the USGS for analysis to avoid having to homogenize and split the sample in the field.

Record detailed notes about soil and surface anomalies, subsample depth, volume, sieving, and other decisions for each sample unit on the field sheets, and label sample containers in the field. If the composite sample needs to be

Protocols for Sampling Solids 5 sieved in the laboratory, make a note on the field sheet and on the sample container (for example, “unsieved bulk composite sample”) in addition to the label with the site name, date, and other information. Note any deviations from the described methods on the field sheet.

Material Containing a Mix of Small and Large Particles

It is not uncommon to have mine waste that is a mixture of fine material (<2 mm) and larger pieces (between 2 mm and 30 cm), such as in an ore stockpile that has had some initial bulk crushing but was never milled. In these piles, the <2 mm fraction and the >2 mm fraction are important to collect and analyze. Site history will help determine whether the >2 mm fraction is important to collect. Two composite samples will be collected at each sample unit, not including duplicates (described in the “Duplicates and Blanks for All Solid Sample Types” section) and additional grab samples.

The approach consists of sieving the material to <2 mm, retaining the >2 mm fraction, and additional processing for larger pieces of material, as needed, to prevent a single large piece from biasing the composition of the >2 mm fraction. The two fractions will provide end-member compositions for the overall waste pile.

Personal Protective Equipment

• Eye protection—Wear safety glasses if the material is large enough to require rock chipping.

• Additional PPE may be required (for example, masks, eye protection, and clothing covering) depending on the site conditions and hazards.

Equipment

• Shovel.

• Rock hammer, small sledge, and (or) pickaxe.

• Trowel, small shovel, or incremental sampler (stainless steel or plastic is necessary to prevent metal contamination).

• 5-gallon plastic buckets (2 per sample unit; one for the <2 mm fraction and one for the >2 mm fraction).

• Large (1 gallon) plastic bags or other spill-proof containers.

• Labels and permanent markers.

• 2 mm plastic or stainless-steel sieve.

• Flagging tape and (or) pin flags to mark subsample locations. Consider the choice of color so that the flags stand out in the sampling landscape.

• Wire brush to remove particles from the sieve as needed in between samples.

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Do not use tap water.

• Paper towels or laboratory wipes.

Rinse sampling tools, sieve, and buckets with DI water and air dry before sample collection.

Subsample Depth and Amount Collected If the material allows, a test hole will yield valuable information about material size and distribution. If some of the material is larger than 10–15 cm in diameter or length, it may be challenging to dig, and a surficial sampling approach will suffice. However, it is important to confirm, if possible, that the surficial material is not a cover on top of the mine waste.

Collect each subsample within a sample unit to the same depth and volume using the same equipment. The amount collected for each subsample can be approximated using the sampling equipment, a bag, or other container, as long as the same amount of sample is consistent at each subsample location. For this material type, a shovel or similarly sized container is usually a reasonable tool to estimate the sample amount, unless the material is mainly fine-grained, then a trowel can be used. It is not necessary to weigh each subsample. Collect enough material to yield about 50 g at each subsample location for both the <2 mm and >2 mm fractions. If the material is mainly fine grained, this protocol will be functionally similar to the tailings protocol, except that the >2 mm fraction is retained. If the material has a larger proportion of >2 mm material, ensure the subsample is large enough to collect about 50 g of <2 mm material at most locations. Ensure the total mass of each composite sample (<2 mm and >2 mm) after all 30 or more subsamples have been combined is at least 1–2 kg each, dry weight.

Compositing Subsamples, Sieving, and Processing Greater Than 2 Millimeter Fraction

Collect the <2 mm and >2 mm fractions of the sample in two separate buckets. If possible, sieve each subsample to <2 mm directly into a bucket in the field. Retain the material that does not pass through the 2 mm sieve and process as follows:

• If most of the >2 mm fraction retained on the sieve is less than approximately 4 cm in diameter and is about 50 g worth of material, it can be placed directly into the second bucket. If this fraction is substantially more

6 Earth Mapping Resources Initiative Protocols than approximately 50 g of material, select an about (~) 50 g randomized subset of material, place it into the second bucket, and discard the remainder. It is important to not bias the selection toward items of a particular size or color; ensure the subset of material is representative of the bulk >2 mm material.

• If there are pieces larger than approximately 4 cm, remove them from the shovel directly and place them aside. Large pieces of material can bias the overall composition of a composite sample and need to be reduced in size to be included in the sample. Choose a random selection of large pieces and ensure care is taken to not bias the selection toward items of a particular size or color. Break these large pieces with a sledge or rock hammer and collect a single chip (less than or equal to ~4 cm in length or diameter) in the second bucket.

• If there is a mix of <4 cm and >4 cm pieces in the >2 mm fraction, then use a combination of the two processes. For example, place a random selection of <4 cm pieces in the second bucket, along with ~4 cm chipped samples from the larger pieces.

Subsamples may show different distributions of large and fine material within a single sample unit. Continue to sample at all locations using the same approach, even if it results in <50 g material for a size fraction at a single subsample location. For example, most subsample locations may have a roughly equal distribution of <2 mm and >2 mm fractions, but one subsample location only has 20 cm rocks and no fine-grained material. At this location, collect the rock chips and no fine-grained material. The composite approach normalizes across the individual subsample location variations to collect an average composition across the entire sample unit.

This procedure results in two buckets: one bucket with <2 mm sieved material and one bucket with >2 mm material, including rock chips. The material in each bucket is considered a separate sample. Ensure each composite sample (<2 mm and >2 mm) is at least 1–2 kg, dry weight. Transfer the composite sample from each bucket to different plastic bags that are sealed and labeled with unique identification.

Double- or triple-bagging before shipping will prevent loss of material during transit.

Large Material Predominantly Greater Than 30 Centimeters

Some waste material, such as waste rock, may have very little fine material and only large pieces that can range from several kilograms to many hundreds of kilograms.

For waste material with large pieces, a <2 mm fraction will not be collected. The following sections present a method to subsample large pieces to collect a representative composite sample.

Personal Protective Equipment

• Eye protection—Wear safety glasses if the material is large enough to require rock chipping.

• Additional PPE may be required (for example, masks, eye protection, and clothing covering) depending on the site conditions and hazards.

Equipment

• Rock hammer, small sledge, and (or) pickaxe.

• 5-gallon plastic bucket.

• Large (1 gallon) plastic bags or other spill-proof containers.

• Labels and permanent markers.

• Flagging tape and (or) pin flags to mark subsample locations. Consider the choice of color so that the flags stand out in the sampling landscape.

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Do not use tap water.

• Paper towels or laboratory wipes.

Rinse sampling tools and buckets with DI water and air dry before sample collection.

Subsampling Approach Subsample points likely will fall on large rocks or boulders. To subsample a large rock, use a rock hammer, sledge, or other tool to chip off 3–5 randomly selected pieces of material approximately 4 cm in diameter from the surface of each rock. Place these pieces directly into the bucket, accumulating rock chips across all the subsample locations.

The composite sample will be the mixed rock chips in the bucket from at least 30 subsample locations and at least 1–2 kg dry weight. The composite sample can be transferred to a plastic bag, sealed, and labeled. Double- or triple-bag the sample before shipping to prevent loss of material during transit.

Protocols for Sampling Solids 7

Drill Cores Drilling is not required for site characterization, but if equipment and budget allow, it is encouraged because samples can be collected at depth in the pile. The details of the best equipment, techniques, and PPE for drilling at the site will be at the discretion of the State agency conducting the work.

Tailings and other fine-grained mine waste are good candidate materials for drilling, resulting in a poorly consolidated core with some larger clasts possibly present. The methods described in the “Collecting Composite Samples” section assume the core is relatively unconsolidated and does not need a rock saw to split or collect samples. If the core does not meet this description, a discussion with USGS Earth MRI personnel may be warranted.

Equipment

• Trowel and (or) scoop (stainless steel or plastic prevent metal contamination).

• Rock hammer or other tool to split clasts as needed.

• Plastic buckets or other containers for the composited samples.

• Large (1 gallon) plastic bags or other spill-proof containers.

• Labels and permanent markers.

• Tape measure for measuring sample unit intervals.

• Deionized (DI) water (or equivalent) and a squirt bottle for cleaning equipment. If DI water is not available, distilled water can be substituted. Do not use tap water.

• Paper towels or laboratory wipes.

Rinse sampling tools and buckets with DI water and air dry before sample collection.

Determining Sample Intervals (Sample Units) Within a Core

If available, review core logs to identify where stratigraphic breaks occur in the core and how frequently they occur. Laying the core out to visually identify the stratigraphic breaks is also suggested. If the material is homogeneous, then dividing the core into equal sections along the entire core depth is an option, depending on how many samples per core are reasonable for the budget. It is more likely, however, that there are apparent heterogeneities in the core. These heterogeneities or stratigraphic breaks can define sample units within the core, such that a sample unit includes depths between the stratigraphic breaks. Samples will be composited across a sample unit defined within the core (described in the “Collecting Composite Samples” section), so that composition is not dominated by only collecting individual or interesting layers within the core. Distinct or unusual layers may be used to separate sample units; include these layers in the composite sample. Depending on the stratigraphy of the core, sample units may be of variable lengths. In sample sheets, note the depths and location in the core where sample units begin and end after laying out the entire core. Each sample unit will result in one composite sample.

For highly variable or closely spaced breaks, some judgment will need to be applied to balance the need to define sample units for compositing and capturing every heterogeneity presented in the cores. In addition to composite samples, grab samples are encouraged, particularly if there are distinct layers that are different from the surrounding material.

The grab samples can be collected after the core is split and the composite sample is collected. This method ensures that the composite sample includes the distinct layers, while the composition of the layers may also be captured individually in grab samples. The balance between the number of composite samples and grab samples will depend upon the overall scope of the project, including the number of drill cores, other samples collected (for example, surface composite samples), and sample budget.

Collec…

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