Marsturite, Mn ₃ CaNaHSi ₅ O ₁₅, a new mineral of the nambulite group from Franklin, New Jersey

Marsturite, Mn₃CaNaHaHSi₅O₁₅, occurs as white prismatic crystals on rhodonite and manganaxinite from Franklin, New Jersey. It is triclinic, space group P1 or P1, with a = 7.70(1), b = 12.03(3), c = 6.78(1)A, α = 85.26(35), β = 94.10(26) and γ = 111.04(12)°, Z = 2. Marsturite is isostructural with nambulite. Optical data are: α = 1.686(2), β = 1.691(1), γ = 1.708(1), biaxial (+), 2V = 60°. The most intense reflections in the powder pattern are: 3.18(40), 2.999(80), 2.916(90), 2.725(100), 1.441(40).