Ikorskyite KMn3+(Si4O10)⋅3H2O, a New Mineral from the Khibiny Alkaline Massif (Kola Peninsula)

Ikorskyite KMn3+(Si4O10)⋅3H2O is a new mineral from agpaitic pegmatite of the Kukisvumchorr Mt. (Khibiny Massif, Russia). The mineral forms radial aggregates of light-brown crystals growing on separate quartz crystals or on romanechite crusts in association with barite, donneite-Y, strontionite, natrolite, vinogradovite, manganoneptunite, and organic matter. The mineral is monoclinic (sp. gr. P21/c. a = 5.0714(3) Å, b = 8.2731(5) Å, c = 13.3740(11) Å, β = 93.730(5)°, V = 559.93(5) Å3). The eight most intense lines in the (I-d[Å]-hkl) X-ray diffraction pattern are 55-7.04-011, 41-4.318-110, 100-4.185-11-1, 24-3.956-021, 28-3.339-004, 19-3.095-014, 30-3.014-113, and 70-2.939-12-2. The ikorskyite has a crystal structure of a new type and belongs to the palygorskite group. The mineral is named in honor of Serafim Veniaminovich Ikorsky (1927–2016), a well-known specialist in the field of organic matter and gases of the Kola alkaline province.