This high quality potash feldspar has been continuously mined in the Black Hills for over 80 years. Custer Feldspar is dry processed from large deposits of pure feldspar so no flotation chemicals are used in any of our products from chip sized to fine grind. For decades, this potash spar has been the choice of potters and artisans as well as industrial customers due to its high viscosity during firing and superior refractoriness.