Excerpt from Clays and Shales of Minnesota This bulletin gives the results of an investigation of the clay resources of Minnesota made during 1912 and 1913. In

Excerpt from The Clays and Shales of Virginia West of the Blue Ridge This report outlines the distribution of the clay and shale-bearing forma tions within the

Excerpt from The Foundry Sands of Minnesota Circulars were issued by the Minnesota Survey in 1918 and 1919 on brass sand, quartz sand, foundry loams, and refrac