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Micheal W. George

Publications and source records attributed to Micheal W. George.

10 recordsLinked to original sources
USGS2017

Tellurium

Tellurium (Te) is a very rare element that averages only 3 parts per billion in Earth’s upper crust. It shows a close association with gold and may be present in orebodies of most gold deposit types at levels of tens to hundreds of parts per million. In large-tonnage mineral deposits, such as porphyry copper and seafloor volcanogenic massive sulfide deposits, sulfide minerals may contain hundreds of parts per million tellurium, although the orebodies likely have overall concentrations of 0.1 to 1.0 parts per million tellurium. Tellurium is presently recovered as a primary ore from only two districts in the world; these are the gold-tellurium epithermal vein deposits located adjacent to one another at Dashuigou and Majiagou (Sichuan Province) in southwestern China, and the epithermal-like mineralization at the Kankberg deposit in the Skellefteå VMS district of Västerbotten County, Sweden. Combined, these two groups of deposits account for about 15 percent (about 70 metric tons) of the annual global production of between 450 and 470 metric tons of tellurium. Most of the world’s tellurium, however, is produced as a byproduct of the mining of porphyry copper deposits. These deposits typically yield concentrations of 1 to 4 percent tellurium in the anode slimes recovered during copper refining. Present production of tellurium from the United States is solely from the anode slimes at ASARCO LLC’s copper refinery in Amarillo, Texas, and may total about 50 metric tons per year. The main uses of tellurium are in photovoltaic solar cells and as an additive to copper, lead, and steel alloys in various types of machinery. The environmental data available regarding the mining of tellurium are limited; most concerns to date have focused on the more-abundant metals present in the large-tonnage deposits from which tellurium is recovered as a byproduct. Global reserves of tellurium are estimated to be 24,000 metric tons, based on the amount of tellurium likely contained in global copper reserves and on a 50 percent recovery rate from refinery anode slimes during the commonly used electrolytic process, also known as solvent extraction-electrolytic refining. If the more economical solvent-leach process—a process that does not recover tellurium—is increasingly used in the future to recover lower grades of copper from porphyry and other large-tonnage deposits, then additional high-grade tellurium-rich gold deposits may become new primary sources for tellurium, particularly epithermal vein deposits associated with alkaline magmatism.

Professional Paper↗
USGS2015

Conflict minerals from the Democratic Republic of the Congo—Gold supply chain

The U.S. Geological Survey (USGS) analyzes mineral and metal supply chains to identify and describe major components of material flows from ore extraction, through intermediate forms, to a final product. Supply chain analyses may be used to identify risks to the United States associated with the supply of critical and strategic minerals and metals and to provide greater supply chain transparency so that policymakers have the fact-based information needed to formulate public policy. This fact sheet focuses on the gold supply chain. The USGS National Minerals Information Center (NMIC) has been asked by governmental and non-governmental organizations to provide information about tantalum, tin, tungsten, and gold (collectively known as “3TG minerals” ) processing facilities worldwide in response to U.S. legislation aimed at identifying and removing the supply chain links associated with the trade of these metals and minerals among armed groups in the Democratic Republic of the Congo (DRC) and adjacent countries. Post-beneficiation processing plants (generally called smelters and refineries) for tantalum, tin, and tungsten (3T) mineral ores and concentrates were identified by company and industry association representatives as being the link in the 3T mineral supply chain through which these minerals can be traced to their source of origin (mine). Tungsten processing plants were the subject of the first fact sheet in a series of USGS reports about 3TG minerals, which was published by the NMIC in August 2014 (Bermúdez-Lugo, 2014). Background information about historical conditions and the voluntary due diligence of multinational stakeholders for minerals from conflict-affected and high-risk areas is presented in the tungsten fact sheet. The current fact sheet, the fourth and last in the series about 3TG minerals, focuses on the gold supply chain. Processing of the 3T mineral concentrates requires substantial infrastructure and capital and generally is done at relatively few specialized facilities that are not located at the mine site; primary and secondary processors typically are at separate locations. Gold, however, can easily be processed into semi-refined products at or near the mine site and has a high unit value in any form, which allows it to be readily exported through undocumented channels, making it more difficult to track to the mine or region of origin. To put this in perspective, 30 kilograms (66 pounds) of 83 percent pure gold (20 carat) would form a cube measuring 12 centimeters per side (about the size of a small tissue box) and, at a price of $1,200 per ounce, would be worth nearly $1 million. By contrast, the equivalent value of tungsten concentrates would weigh about 45 metric tons (t) (100,000 pounds). Once conflict sourced gold has been combined with gold from other mines and scrap at a refiner, there is no feasible way to distinguish the source of the gold. Thus, once the gold leaves the immediate area of production, it is nearly indistinguishable from gold products mined in other areas.

Fact Sheet↗
USGS2009

Selenium Recycling in the United States in 2004

The vast majority of selenium consumption in the United States is in dissipative uses, such as alloys, animal feeds, fertilizers, glass decolorizer, and pigments. The nondissipative use as a photoreceptor for xerographic copiers is declining. As a result of a lack of a substantial supply of selenium-containing scrap, there are no longer selenium recycling facilities in the United States. Selenium-containing materials collected for recycling, primarily selenium-containing photocopier drums, are exported for processing in other countries. Of the estimated 350 metric tons (t) of selenium products that went to the U.S. market in 2004, an estimated 300 t went to dissipative uses. An estimated 4 t was recovered from old scrap and exported for recycling.

Circular↗
USGS2009

Mineral resource of the month: gold

The article presents information on the valuable mineral called gold. It states that early civilizations valued gold because of its scarcity, durability and characteristics yellow color. By the late 20th century, gold was used as an industrial metal because of its unique physicochemical properties. The U.S. has several productive deposits of gold, including placer, gold-quartz lode, epithermal and Carlin-type gold deposits.

Earth↗
USGS2006

Mineral resource of the month: tellurium

Global demand for tellurium has grown significantly in recent years owing to increased use in solar cells in the United States and Europe, thermoelectronics (especially in China) and steelmaking worldwide. Estimated global production, however, has remained relatively unchanged over the same period, while accumulated inventories have been exhausted, leading to a supply shortfall.

Geotimes↗
USGS2004

Mineral of the month: indium

Indium was discovered in Germany in 1863. Although it is a lustrous silver-white color, the finders named the new material for the “indigo” spectral lines the mineral created on the spectrograph. Indium ranks 61st in abundance in Earth’s crust and is about three times more abundant than silver or mercury.

Geotimes↗