Custer feldspar supplies SiO2, Al2O3, K2O, Na2O, CaO, and Fe2O3. Commonly used potash feldspar. Can be used to substitute for Keystone, Buckingham, Yankee, or
Kingman feldspars. Manufactured by Pacer Corporation; comes from Custer, SD. Primarily feldspar, some free quartz and traces of iron and magnesium.
(courtesy of glazy.org)
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