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By Shanxi Wu, Jialong Li, Haoyu Hu, Jiqing He, Zhaohui Wang, Bochao An, Shenyi Zhang

There are a large number of thick alluvium and thin bedrock deposits at depth in the Henan coal base. The degree of surface mining is high, and the surface environment is seriously damaged. Using indoor experiments, numerical simulation, and field measurement, it is studied the influence of the mechanical properties of thick alluvium on the surface subsidence characteristics of thick alluvium thin bedrock deposits at depth, taking Zhaogu No. 2 coal mine as the research background. The results show that the compressive strength and elastic modulus of the alluvial layer are linearly negatively correlated with the alluvial layer particle size, linearly positively correlated with the confining pressure, and nonlinearly positively correlated with the loading rate. The thickness of the alluvial layer has the greatest influence on the displacement of surface subsidence and the range of surface subsidence. The advancing mining rate of the working face has the greatest influence on the surface horizontal displacement. The mechanical properties of the alluvial layer affect the evolution characteristics of the caving arch and towering roof beam. The influence range of the 11012 working face is about 550 m, β is about 55.5°, and the maximum subsidence rate of the surface is 12 mm/day. The mining process and separation grouting can be adjusted to control the overburden displacement to reduce surface disturbance and protect the surface ecological environment. The research results of this paper can provide a research basis for the study of surface subsidence under similar geological conditions.

Apr 28, 2024

By Yuqi Zhao, Zhiyong Lin, Leiting Shen, Hongyang Wang

Gibbsite-type bauxite is the main material for alumina extraction by Bayer process globally, while the iron in red mud is difficult to use for the high alumina content. Therefore, the efficient separation of iron and alumina is the premise for the resource utilization of red mud. In this work, the separation of iron and alumina in red mud containing 47.45% Fe and 11.58% Al2O3 was studied through reduction roasting followed by magnetic separation. The analysis methods of XRD, VSM, SEM, and EDS were used to investigate the phase transformation of red mud during reduction roasting. Results show that hematite can be firstly reduced into magnetite, and alumogoethite into magnetite and alumina. Then, the magnetite reduction undergoes the process of Fe3O4→FeO→Fe, while alumina can react with FeO to form hercynite. The hercynite is ultimately reduced into metallic iron and alumina at elevated temperature. The specific saturation magnetization of reduced product is closely related to its main minerals, that is, the specific saturation magnetization of magnetite and metallic iron is higher than that of wustite and hercynite. The mass ratio of Fe to Al2O3 in magnetic concentrate increases with roasting temperature, from 4.55 at 600 °C to 10.27 at 1200 °C. Therefore, efficient separation of iron and alumina in red mud could be achieved through deep reduction-magnetic separation.

May 2, 2024

By Li Yuab Chi, Rikard Mäki, Riika M. Ylitalo, Pekka Bergström, Zong‑Xian Zhang, Sunniva Haugen, Anders Sand

The effect of detonator placement on rock fragmentation by blasting was studied in the Kevitsa open-pit mine. Considering rock mass properties, explosives properties, and blast parameters, a comprehensive analysis of 37 production blasts confirms that the middle detonator yields finer fragmentation than the bottom detonator in the full range of investigated sizes. Meanwhile, using the LS-DYNA code, a bench model with a single blasthole was built in a three-dimensional setting. A single detonator placed at two different positions—the middle and bottom—of the explosive column was analyzed in this study. By analyzing principal stress states on the plane through the blasthole axial and vertical to the bench face, the numerical results show that the middle detonator creates a stress concentration area near the bench face characterized by triaxial tension, while the bottom detonator does not. Furthermore, the middle detonator generates a larger stress concentration area with biaxial tension near the bench face than the bottom detonator. Considering that triaxial and biaxial tensions are more favorable to fragmentation than uniaxial tension, it can be concluded from simulation results that these areas with triaxial tension and biaxial tension in the middle detonator are a significant factor contributing to achieving better fragmentation, compared to the bottom detonator. The middle detonator position has replaced the bottom detonator position in the Kevitsa mine.

May 20, 2024

By Jiaqi Jin, Jan D. Miller, Chen‑Luh Lin, Amanda N. Erskine, Shijie Wang

Recovery of metals from coarse ore particles is a great challenge for heap leaching operations of low-grade precious metal resources. Internal fractures of ore particles like micro-cracks can facilitate subsurface transportation of solution inside particles and leaching of valuable minerals. A plant-scale high-pressure grinding roll (HPGR) unit at Coeur Mining’s Rochester mine was operated at selected specific pressures to crush and prepare various products for crack analysis using high-resolution X-ray computed tomography (XCT). 3D shapes of cracks inside ore particles for selected size fractions reveal different damage mechanisms during HPGR crushing regarding particle size and crushing pressure. Close-to-surface cracks formed by abrasion were found in small 2.5 mm particles. Impact cracks with a high aspect ratio were found in particles of larger size and higher HPGR pressure. The volumetric percentage of internal fractures and the specific crack surface areas of selected ore particles are compared to give quantitative conclusions on particle damage by compression during HPGR crushing.

Apr 20, 2024

By Taghi Sherizadeh, Samuel Nowak, Kutay Karadeniz, Paul Brooks, Alper Kirmaci, Mina Esmaeelpour, Dogukan Guner, Gunnar Wurst

As mines continue to deepen and become more expansive, active monitoring of larger volumes of rock mass will become more critical to calibrate numerical simulations and to ensure the safety of underground workers. Monitoring larger volumes of rock mass requires low-cost sensors which are simple in construction and installation. In this study, a novel hybrid optical fiber cable (HOFC) designed for use in distributed optical fiber sensing (DOFS) via grouted boreholes was employed to monitor a bulk mining operation in an underground metal mine. The HOFC was successfully used to monitor approximately 2.7 × 103 m3 of rock mass above excavations surrounding a pillar removal area in which six large pillars were removed simultaneously. A total of six measurement boreholes (maximum depth of 22 m) were used to measure strain along the optical fiber during the pillar removal operation using the HOFC, allowing for 70 individual strain measurement points, which were constructed for under one US dollar each. Monitoring of the excavation area took place over a 44-day period after pillar removal. Extensional strains were noted in the areas closest to the removed pillars, while areas of compression were noted directly above the remaining pillar in the area. The results of the case study demonstrate that a low-cost optical fiber strain sensing network can be rapidly installed in a large excavation area and can provide highly sensitive strain measurements in a manner that would be cost-prohibitive via other methods.

May 13, 2024

By Sidi Deng, Sharon Pedraza, Aaron Noble, Subodh Das, Bin Ji, Wencai Zhang, Michael Van Brunt

In this study, a MSWI bottom ash sample was assessed to evaluate the feasibility of various physical beneficiation processes in concentrating valuable elements prior to chemical leaching. The raw sample was initially assayed to determine the content and economic value of various metals present in the material. The potential recoverable value (PRV) of the sample was calculated, and the result showed that the total PRV of the sample was 483 $/ton, with Ti, Sc, Fe, Cu, and Zn being the most valuable metals. Next, various physical separation processes, including size fractionation, froth flotation, magnetic separation, and gravity separation, were conducted to determine the extent to which the valuable elements can be concentrated. The results were compiled into an element-by-beneficiation enrichment ratio (er) matrix that was used to develop suitable beneficiation flowsheets for further consideration. The result clearly show delineation of four products, including a Fe-rich product that can be isolated by magnetic separation (er = 5.0), a Cu/Zn-rich product that can be isolated by flotation (er = 5.3 to 9.4), a Sc-rich product that can be isolated by gravity separation (er = 0.6), and a Ti–rich product that is produced in the residue. Lastly, the leachability of valuable elements from the bottom ash sample was determined by acid leaching tests. The results indicated that it is viable to employ hydrometallurgical methods to recover and purify the valuable metals. This work provides a reference for the recovery of valuable metals from MSWI bottom ash from both the technical and economic aspects.

Apr 27, 2024

By Lars Hultman, Abu Yaya, Gabriel K. Nzulu, Per Eklund, Martin Magnuson, Prosper M. Nude, Hans Högberg

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons. org/licenses/by/4.0/.

Apr 3, 2024

By Aaron Noble, Mahmud Esad Uluer

Respirable coal mine dust (RCMD) is one of the biggest occupational health hazards for underground coal miners. Dusty mining environments can cause long-term health problems, including pneumoconiosis and progressive massive fibrosis. The Mine Safety and Health Administration (MSHA) has recently revised regulations promoting enhanced dust mitigation technologies, which have sparked renewed interest in the development of dust mitigation technologies. The flooded bed dust scrubber (FBS) is one of the most widely used technologies; however, it is limited by technical challenges, the most notable being the potential to clog. Recent studies have shown that applying vibration to filter mesh can improve the overall efficiency of the scrubber and that the system can be readily integrated to existing continuous mining equipment using an energy harvesting approach. In this follow-up study, the impact of mesh design and surface modification on system efficiency was examined using different vibrating liquid-coated stainless-steel mesh panels in a laboratory-scale FBS. Based on the two-way interaction data from a multi-factor experimental design, the results show that the performance of the system can be optimized by using hydrophilic 20- or 30-layer filters and by excitation frequencies between 67 and 134 Hz. This laboratory study suggests that a 20-layer mesh screen with hydrophilic surface applications and optimized vibration parameters can perform similar to that of a 30-layer static mesh, which is typically used in industrial units.

May 23, 2024

By Hong Yong Sohn, Xiaoyi Cai, Wei Wang, Liangzhao Mu, Fengqin Liu, Hongliang Zhao

Thebottom-blownsmeltingtechnologyhasbeenwidelyadoptedinnon-ferrousmetalsmeltingindustries.Thelargestbottomblown smelting furnace used in copper smelting was numerically simulated to improve the stirring effect in the molten bath by optimizing the oxygen injector arrangement and blowing parameters. The results show that a small injector spacing leads to gas jet coalescence, which is detrimental for smelting efficiency, increases copper loss and shortens furnace service life. Three schemes were proposed to improve the uneven stirring and reduce the gas jet coalescence by increasing the axial spacing of the injectors, the radial installation angle and the gas injection angle. Changing the axial spacing of the injectors can significantly reduce the gas jet coalescence, yielding the best stirring effect. The results of simulation suggested that when the axial spacing of the injectors was increased from 0.380 m to 0.610 m, the mean melt velocity in the mixing zone increased to 0.243 m/s, which was 20.9% higher than that before the optimization. Meanwhile the RSD (relative standard spatial deviation of melt velocity) decreased from 123% to 84%. In the actual production, the matte content in the smelting slag decreased from 6.57% to 3.12% after changing the axial spacing of the injectors from 0.380 m to 0.610 m.

Apr 10, 2024

By Danu Putra, Budi Sulistianto, Tri Karian, Mohammad Nur Heriawan

Stope layout optimization is an important feature of underground mining that maximizes the economic value of the project while taking mining limits into account. The large number of parameters and constraints makes it difficult to obtain the optimum condition. Several algorithms have been created to address these problems using a variety of methods. However, the circulating method has not explicitly included stope dimension stability analysis, resulting in a solution that is not stability-proven, which can result in a suboptimal solution. This study integrates the Mathews stability graph into the stope optimization algorithm so that the optimized stope layout considers stability conditions directly through an assessment of the available geomechanical data within the block model. The proposed algorithm is validated through a case study of a synthetic block model created by considering variations in grade and the geomechanical conditions of the rock. Furthermore, several scenarios are created to compare the performance of the algorithm that applies variations in stope sizes with the common case study of stope sizes that remain fixed. A more detailed assessment is also conducted on each final stope layout wall to ensure the successful application of stability analysis in the proposed algorithm through back analysis on the Mathews stability graph. The optimization results show that all walls in the final stope layout fall into the stable condition. Also, the proposed algorithm is also capable of maintaining the project’s economic value. Ultimately, the proposed algorithm can be deemed applicable and suitable for use in the initial stages of mining as a comprehensive assessment of the optimal stope layout, taking into account the stability conditions of the stope.

May 22, 2024

By Shankar Kumar, Arvind Kumar Mishra, Chitranjan Prasad Singh

Formulating a predictive model for blast-induced ground vibration (BIGV) has always been challenging due to the complex non-linear relationship between the BIGV and its influencing factors. Researchers have used empirical, artificial intelligence methods and numerical modelling methods to predict BIGV. In a dragline bench blasting, a massive quantity of explosives is used compared to other loading machinery, and the height of the bench depends on the size of the dragline. For effective utilization of explosives energy, decking is used to reduce the hazardous effects of blasting. In this paper, an attempt has been made for effective prediction of BIGV, and its mitigation on dragline bench blasting considering a deck length, stiffness ratio, hole spacing to burden ratio, hole depth to burden ratio, the distance of monitoring PPV from blasting site, Schmidt hammer rebound number of the bench to be blasted, and maximum charge per hole to total charge per blast. So artificial neural network (ANN) model and random forest (RF) model have been developed considering the parameters mentioned above. For the statistical performance of the predictive model, the coefficient of determination (R2) value is 0.8895, MSE is 22.84 for the ANN model, and the random forest (RF) model whose R2 is 0.8165 and MSE is 27.18. The sensitivity analysis results show that stiffness ratio, deck length, and Schmidt hammer rebound number are more influential parameters out of the selected parameters. The reduction of ground vibration with the introduction of decking led to a 3 to 15% reduction in ground vibration.

May 15, 2024

By A. A. El‑Midany, O. M. Asem, S. E. El‑Mofty, M. F. Abadir

Glauconite is a clay mineral that is most probably mined with phosphate and represents a challenge for phosphate upgrading by flotation. Reverse flotation is a common method for removing silica and silicate from siliceous phosphate. Thus, a systemic study was conducted to determine the effect of clay and its interactions with siliceous phosphate ore components on its cleaning by flotation. The flotation of each mineral (phosphate, quartz, and clay) was tested in terms of product recovery using quaternary amine at pH 9. In addition, the settling behavior of each mineral was investigated with and without quaternary amine. Binary and tertiary systems were studied to investigate the interactions between the main ore-containing minerals. The results of each mineral flotation test showed that quartz has the highest floatability, with low floatability of both phosphate and glauconite by quaternary amine. The presence of glauconite does not affect the phosphate recovery, whereas glauconite reduces the quartz floatability, which deteriorates the quartz removal from phosphate. Finally, the interaction mechanisms in the different systems are illustrated.

Apr 5, 2024

By Ben Kudakwashe Mperekwa

Core logging represents one of the most critical control points in mineral exploration, serving as the stage in which geological observations are transformed into structured data that underpin interpretation, modeling and economic decision-making. Every geological model and resource estimate ultimately depends on how accurately drill core is logged, recorded and managed. Despite its importance, core logging is frequently treated as a routine operational activity rather than a data-critical process. In practice, inconsistencies in logging approaches, subjective interpretation and weaknesses in data management can introduce errors that propagate throughout the exploration workflow. These errors often remain undetected until later stages, where they can significantly affect model reliability and project evaluation. As exploration programs become increasingly data-driven, there is a growing need to improve not only how geological data are collected, but also how they are structured and integrated into downstream workflows. This article presents a practical overview of core logging practices, examines the evolution of logging systems and highlights key challenges and opportunities for improving data reliability from field logging through to resource estimation.

Aug 1, 2026

By William Gleason

Founded in 1891, Hecla Mining Company is the oldest precious metals company on the New York Stock Exchange and the largest primary silver producer in the United States and Canada. An innovative mining method at its historic Lucky Friday Mine in Idaho coupled with a low-cost, high-margin operation at its Greens Creek Mine in Alaska and production growth opportunity at the Keno Hill Mine in Canada’s Yukon Territory has positioned Hecla well for a period in which silver has retraced from its January all-time high but continues to hold above the previous cycle’s peak pricing. And while some precious metal producers have looked for expansion into other commodities, Hecla has turned its focus to its core identity as North America’s premier primary silver producer. In April, Mining Engineering had the opportunity to visit the Lucky Friday Mine. For more than eight decades, Lucky Friday has operated in one of North America’s most productive and geologically challenging silver districts, Idaho’s famed Silver Valley. As mining advanced deeper into the vein system, the same geological forces that created exceptional mineralization also produced increasing seismic hazards at the mine. This challenged the company to find a new way to manage the growing stresses associated with depth. Hecla found its answer with the deployment of the underhand closed bench (UCB) mining method, which was developed and implemented at Lucky Friday. The UCB method uses large-scale, deephole blasts to proactively trigger seismic events. The blasts destress the zone while fracturing the ore. More than 90 percent of the area’s seismic energy is released within a 12-hour window. “The constraint that resulted in the development of UCB was seismicity related to a corner geometry between two stopes,” Chris Neville, vice president and general manager of the Lucky Friday Mine, told Mining Engineering. “It was a well-understood seismically active area and was being managed by a common technique by withholding miners from the area after a blast. A very similar situation in the Lucky Friday vein in the 1990s had been managed using a destressing technique. The destressing would eliminate the need to withhold miners to keep them safe and return the stope back to double-shift rather than single-shift production. A blast pattern was executed and achieved the desired effect but also led to the question “What would happen if there were just a few more holes in the blast?” Hence, the UCB concept was sparked, which eventually spread to the rest of the seismically problematic mining areas and the main mining front on the Gold Hunter 30 Vein.” The UCB method changed the way things were done at Lucky Friday and the method received a number of industry accolades, including the prestigious Robert E. Murray Innovation Award from the Society for Mining, Metallurgy & Exploration (SME) in 2022. The story of UCB is one of the most recent advancements in a decades-long effort to push deeper into one of the world’s most complex underground mining environments while improving safety, productivity and workforce utilization.

Aug 1, 2026

By SME

The 44th Annual American Mining Hall of Fame Awards Banquet and Fundraiser, sponsored by the Mining and Minerals Education Foundation (MMEF), will be held Dec. 5, 2026, in Tucson, AZ. Proceeds from the event will fund an Education Outreach Program managed through The University of Arizona School of Mining Engineering and Mineral Resources. Each year, the MMEF honors a slate of individuals and companies who have made notable contributions to the advancement of the mining industry.

Jul 1, 2026

By Gregory Abramov

Borehole mining (BHM) is a remotely operated waterjet mining method carried out through wellbores drilled and cased from the surface directly into the production interval. Mining operations are performed using a waterjet tool composed of at least two concentric tubular columns, which create two hydraulic passages: one for pumping high-pressure water down, and the other for transporting the produced slurry to the surface. At the lower end of the dual column, a bottom head is installed, equipped with a hydromonitor that generates a powerful water jet, and an eductor (jet pump). The tool is suspended from a drill rig via a swivel, enabling its rotation and advancement along the borehole. While the waterjet continuously cuts the rock and produces slurry, the eductor lifts the slurry to the surface. In a slurry collection tank or pond, the cuttings are separated and the clarified water is recycled. As ore is extracted, BHM stopes are typically formed that may remain open for an extended time before caving in.

Jun 1, 2026

By Greg Rankin

With commodity prices rising across the mining sector, from gold to strategically critical rare earth elements, more material has moved back into economic consideration. This has placed greater emphasis on reliable and defensible analytical results. When gold reached record levels earlier this year, material long considered marginal was suddenly worth another look. Stockpiles were revisited, lower-grade zones returned to the model, and economic assumptions were recalculated in light of a new price reality. That recalibration narrows the margin for analytical uncertainty. As projects operate closer to economic thresholds, small differences in assay results begin to carry greater weight across exploration programs, grade control and processing decisions. In many operations, the line between sending material to the mill or to the dump hinges on fractions of a gram per ton. This is true in gold projects adjusting cutoff grades or in rare earth deposits managing complex elemental distributions. At that scale, analytical data do more than confirm grade; they shape classification, recovery modeling and longterm resource estimates. No reserve is declared without defensible analytical data supporting the underlying resource model. In projects operating near cutoff, those laboratory results directly influence economic classification decisions. “The difference between a viable project and a marginal one can come down to analytical precision,” said William R. Sattlegger, P. Geo., chief executive officer of i2iVestcom Advisors Corp. and executive director of the Critical Minerals Conference. “Those numbers drive metallurgy, recovery and valuation models. If you lose confidence in the data, you lose confidence in the project.” Consider a deposit processing 20 Mt (22 million st) annually at a cutoff near 0.5 g/t. A shift of just 0.05 g/t in reported grade, whether from sampling variability or calibration bias, can alter how large volumes of material are classified. Across that scale, even small analytical differences can translate into meaningful economic consequences.

Jun 1, 2026

By Justin Vandenbrink, Ray DeLuna

In many mine development schedules the critical path is generally defined by ore definition, permitting, infrastructure design, equipment procurement and initial production. While permitting is recognized as a schedule driver, water-related baseline characterization and permitting are often underestimated within that process. When addressed explicitly, they can be reduced to a single line item scheduled to conclude shortly before operations begin, rather than treated as the long-lead dependency they often become in practice. That assumption has delayed projects, inflated capital costs and in some cases stopped development entirely. Water-related permitting is not a discrete step. It is a sequential, datadependent regulatory process that begins with baseline characterization, proceeds through multiple layers of agency review and often across multiple overlapping state and federal regulatory pathways. This article examines the disconnect between how mine development critical paths are typically defined and the influence water-related decisions ultimately have on schedule, capital and longterm liability. The evidence comes from two case studies: an ISR uranium project in Wyoming navigating a threetrack permitting process, and an abandoned copper mine in California where water liability is still being resolved years after operations ceased. Together, they illustrate a consistent principle: water is always on the critical path. The teams that manage it well simply start earlier.

Jul 1, 2026

By S. Harteis, D. Dolinar

Many mining operations rely on bulkheads to provide a barrier between impounded water or slurry and active mine workings. However, bulkhead failures could cause and have caused catastrophic flooding that puts the underground workforce at risk. The National Institute for Occupational Safety and Health1 (NIOSH) in collaboration with the Mine Safety and Health Administration (MSHA) is conducting research to evaluate the adequacy of existing design practices for water and slurry bulkheads. A key component of this research effort is documentation of the performance history and design parameters for bulkheads installed in underground coal mines during the last 20+ years. This research is part of a larger effort to develop general design guidelines and procedures for constructing and maintaining bulkheads that will help to ensure their long-term structural integrity, while significantly reducing the inundation risk for miners. This paper presents the results of NIOSH’s research to identify state-of-the-art bulkhead designs, including design criteria, leakage monitoring systems, and emergency warning systems. Underground observations and evaluations of existing bulkheads suggest that the most important design factors influencing their performance are the interface of the bulkhead with the surrounding strata and the potential magnitude of the hydraulic pressure to which they may be subjected. When a bulkhead has failed, leakage has generally been through the surrounding strata or along the bulkhead/strata interface, with the failure potential along the interface increasing with hydraulic head. It was also determined that development of a monitoring program to ensure the long term structural integrity of bulkheads is an important safety consideration. Current monitoring procedures range from weekly visual inspections to constant monitoring via pressure transducers and fluid level indicators. Where possible, these devices are used in conjunction with a computer based mine monitoring system to alert mine personnel when an emergency condition exists at the bulkhead installation.

Jan 1, 2006

By Jianmin Qin, Raja V. Ramani, Wilson Miola

The number of underground work entities operating under reduced dust standards in U.S. coal mines has been increasing since the start of the decade of the 80s and is currently approaching 10,000. The concern for controlling the quartz levels in airborne respirable dust in coal mine has manifested itself in several improvements in equipment selection and operation, face ventilation practices, and dust control procedures. At the same time, fundamental studies have been initiated on determining the source-sink relationships of the airborne quartz dust. The P-7 method is the prescribed method for the determination of quartz in the respirable airborne dust samples from coal mines. Questions have been raised on the reliability of the P-7 infrared spectrometry method for quartz analysis in powders. No specific method has been defined for quartz determination in bulk samples from the mine. In a recent study on the relationship between quartz in the airborne dust and that in the materials being mined, both infrared (IR) and x-ray diffraction (XRD) methods were used on a suite of samples from several coal mines. These samples encompassed airborne respirable dust samples, airborne total dust samples, the oversize fraction from the respirable samplers, ROM samples, channel samples, and chip samples from the face, roof, and floor materials. In this paper, the sample preparation and analysis procedures for the samples are discussed. The data, analysis results, and comparisons of the P-7 and XRD results are presented. The quartz percent determined for the same sample by the two methods are different. In 85% of the samples analyzed, the quartz percents determined by the XRD method are higher than those obtained by the P-7 method. However, there is a strong linear relationship between the results from the two methods. Further, the XRD method indicates an average of 20 percent more quartz than that from the P-7 method. The reasons for the differences in the results and the need for additional studies are explored.

Jan 1, 1991