Dobrovolskyite, Na4Ca(SO4)3, is a new sulfate mineral from the Great Tolbachik fissure eruption, Kamchatka peninsula, Russia. It occurs as aggregates of tabular crystals up to 1–2 mm in maximum dimension, with abundant gas inclusions. The empirical formula calculated on the basis of O = 12 is (Na3.90K0.10)Σ4(Ca0.45Mg0.16Cu0.12Na0.10)Σ0.83S3.08O12. The crystal structure of dobrovolskyite was determined using single-crystal X-ray diffraction data as: trigonal, R3, a = 15.7223(2), c = 22.0160(5) Å, V = 4713.1(2) Å3, Z = 18 and R1 = 0.072. The Mohs’ hardness is 3.5. The mineral is uniaxial (+), with ω = 1.489(2) and ɛ = 1.491(2) (λ = 589 nm). The seven strongest lines of the powder X-ray diffraction pattern [d, Å (I, %)(hkl)] are: 11.58(40)(101); 5.79(22)(202); 4.54(18)(030); 3.86(88)(033); 3.67(32)(006); 2.855(50)(306); and 2.682(100)(330). The mineral is named in honour of Prof. Dr. Vladimir Vitalievich Dolivo-Dobrovolsky (1927–2009), one of the leading Russian scientists in the field of petrology, crystal optics and crystal chemistry. The crystal structure of dobrovolskyite can be described as composed of three symmetrically independent rods running parallel to the c axis. The rods consist of six octahedral–tetrahedral [Na(SO4)6]11– or [Ca(SO4)6]10– clusters of central octahedra sharing common corners with six adjacent SO4 tetrahedra. Alternatively, the crystal structure of the mineral can be described as a 12-layer ABACABACABAC eutactic array of Na+ and Ca2+ cations, and vacancies with disordered (SO4) tetrahedra in interstices. Dobrovolskyite and similar minerals probably formed upon cooling of a high-temperature phase with disordered cation and anion arrangements.

Dobrovolskyite Na 4 Ca（SO 4）3是一种新的硫酸盐矿物，来自俄罗斯堪察加半岛的大Tolbachik裂隙喷发。它以最大尺寸可达1-2 mm的板状晶体的聚集体形式存在，并带有大量的气体夹杂物。的O = 12的基础上计算出的经验式是（钠3.90 ķ 0.10）Σ4（钙0.45镁0.16铜0.12钠0.10）Σ0.83小号3.08 Ò 12。使用单晶X射线衍射数据确定三硼硅藻土的晶体结构为：三角形，R 3，α= 15.7223（2），C ^ = 22.0160（5）A，V = 4713.1（2）埃3，Ž = 18和- [R 1 = 0.072。莫氏硬度为3.5。矿物是单轴（+），ω= 1.489（2）和ɛ= 1.491（2）（λ= 589 nm）。粉末X射线衍射图的7条最强线[ d，Å（I，％）（hkl）]是：11.58（40）（101）; 5.79（22）（202）; 4.54（18）（030）; 3.86（88）（033）; 3.67（32）（006）; 2.855（50）（306）; 和2.682（100）（330）。该矿物以纪念弗拉基米尔·维塔利耶维奇·多利沃·多布洛沃斯基（Vladimir Vitalievich Dolivo-Dobrovolsky教授，1927–2009年）的名字命名，弗拉基米尔·维塔利耶维奇·多利沃·多布罗沃斯基（Vladimir Vitalievich Dolivo-Dobrovolsky）教授是俄罗斯岩石学，晶体光学和晶体化学领域的领先科学家之一。白云母的晶体结构可以描述为由平行于c轴的三个对称独立的棒组成。棒由六个八面体-四面体的[Na（SO 4）6 ] 11–或[Ca（SO 4）6 ] 10–组成的八面体中央簇，与六个相邻的SO 4共享公共角四面体。或者，矿物的晶体结构可以描述为Na +和Ca 2+阳离子的12层ABACABACABAC共晶阵列，以及空隙中具有无序（SO 4）四面体的空位。多溴代沃石和类似的矿物可能是在冷却具有无序阳离子和阴离子排列的高温相时形成的。