Murataite, a new complex oxide with the general formula (Na,Y,Er)4(Zn,Fe)3(Ti,Nb)6O18 (F,OH)4, occurs in a pegmatite in the St. Peters Dome area, Colorado. The mineral is cubic, spaCe group F432, Fm3m, or Fm3; a = 14.863(5) Å Z = 8. Strongest lines of the X-ray pattern are: 8.51(3), 2.858(10), 2.468(6), 1.746(8), 1.489(8), and 1.432(5).
Megascopically the mineral is black and submetallic; in polished section it is gray in white light, darker in oil. The reflectance is 13.6 ± 0.14 percent (air) at 546 nm wavelength. Murataite is translucent and brown in thin section, and is isotropic to very weakly anisotropic; n (est) = 2.13. Microhardness HV100 = 827. Density (meas) = 4.69 g/cm3; (calc) = 4.64 g/cm3.
Murataite is a very rare accessory in a pegmatite of complex mineralogy that is probably derived from the alkalic Mount Rosa Granite.