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The chemistry of eolian quartz dust and the origin of chert Temporal and spatial sources of silica for chert remain poorly constrained. Modern sources to the worlds oceans include silica in rivers > aeolian (dust) deposition > sea floor vents and submarine weathering. However, changes in aridity and dust flux during the Phanerozoic may explain variations in the ocean silica cycle and times and places of chert formation. The chemistry of fine quartz dust (FQD) provides a chemical mechanism for the transformation of FQD to polymorphs of silica in chert; FQD is readily dissolved, then reprecipitated as Opal-A by either biotic or abiotic processes. An unequivocal relation between increases in dust flux and biogenic opal-A in the western Pacific Ocean during the past 200 kyr... Tags: Africa, Energy Resources, Geochemistry, International, Soil Sciences, All tags... USGS Science Data Catalog (SDC), aridity, chalcedony, chemistry, chert, deposition, dust, eolian, flocculates, gypsum, loess, microcrystalline, opal, porcellanite, quartz, silica polymorphs, silt, wind, Fewer tags Point locations of brick kilns in Kabul, Afghanistan, derived from 1965, 2004, 2011, and 2018 satellite imagery This dataset was created as part of the USGS Afghanistan Project investigating artisanal and small-scale mining activity. Clay mining for brick making purposes represents a small but important segment of the mineral extraction industry in Kabul, Afghanistan. Over the past several decades Kabul has grown from a relatively small city, with a 1970 population of less than 500,000 people, to a sprawling urban center with approximately 4.2 million people in 2020 (CIA 2020). Population growth has expanded the need for housing, commercial, and industrial buildings, and associated infrastructure. This has greatly increased demand for bricks, the primary construction material of the region. In this study, very high-resolution... Categories: Data; Types: Downloadable, Map Service, OGC WFS Layer, OGC WMS Layer, Shapefile; Tags: Afghanistan, Geography, Loess, Mineral Resources, USGS Science Data Catalog (SDC), All tags... biota, clay deposits, mining and quarrying, Fewer tags