The Mercer Clay bed in central Pennsylvania has produced feedstocks for the refractory industry in the USA and has also been investigated as a source of alumina and lithium. Developments in global markets for these commodities, as well as rare earth elements, have led to their classification as critical minerals in the USA, in turn renewing production opportunities for the Mercer Clay resource. The work reported here includes a review of the clay types and minerals involved, as well as past mineral processing and extractive metallurgy test work, and reports new research results from renewed investigation of the deposit as a polymetallic resource. This renewed work has found lithium contents that exceed 1,000 ppm, lying directly below the overlying Mercer coal, where the alumina content ranged from 32 to 34 wt%. Total rare earth concentrations were somewhat lower than have been found elsewhere in the region, and the highest contents were also found to be stratigraphically close to the coal. Further work is required to establish the mineral hosts for lithium and rare earths and to define the extent of enriched alumina, lithium, and rare earth concentrations.

宾夕法尼亚州中部的 Mercer 粘土床为美国的耐火材料工业生产原料，也被研究作为氧化铝和锂的来源。这些商品以及稀土元素的全球市场的发展导致它们在美国被归类为关键矿物，反过来又为美世粘土资源更新了生产机会。此处报告的工作包括对所涉及的粘土类型和矿物的回顾，以及过去的矿物加工和提取冶金测试工作，并报告了重新调查该矿床作为多金属资源的新研究成果。这项更新的工作发现锂含量超过 1,000 ppm，直接位于上覆的 Mercer 煤下方，其中氧化铝含量范围为 32 至 34 重量％。总稀土浓度比该地区其他地方发现的略低，而且最高含量也被发现在地层上靠近煤。需要进一步的工作来建立锂和稀土的矿物宿主，并确定富集氧化铝、锂和稀土的浓度范围。