Santafcite is a new hydrated vanadate found in the Grants uranium district, McKinley County, New Mexico, in the spring of 1951. It has the formula Na2O·3MnO2·6(Mn,Ca,Sr)O·3(V,As)2O5·8H2O. The mineral occurs as an encrustation of small rosettes of acicular crystals on an outcrop joint surface of Todilto limestone. Physical and optical properties are: perfect (010) and distinct (110) cleavages, very brittle, measured density 3.379, black color, brown streak, subadamantine luster, readily fusible in an alcohol flame to a dull black bead; translucent only in very small fragments, pleochroic from dark reddish brown to yellowish brown, with absorption X>Y>Z; X = c, α = 2.01, and distinct dispersion. X-ray studies by rotation, Laue, Weisscnberg, and powder diffraction methods indicate orthorhombic symmetry, space group B2212, D25, with cell dimensions: a0 = 9.25±.02 Å, b0 = 30.00±.02 Å; c0 = 6.33±.02 Å.
The mineral is named santafeite, after the Atchison, Topeka and Santa Fe Railroad Company, in recognition of its pioneer exploration and development of the uranium deposits in New Mexico.