Vrančiceite is a new mineral species discovered in a sample collected from the old mine dumps of the abandoned Vrančice deposit near Příbram, central Bohemia, Czech Republic. Vrančiceite occurs as rare anhedral grains, up to 100 μm in size, in a calcite gangue, associated with cinnabar, djurleite, galena and hedyphane. Vrančiceite is black, with metallic lustre. Mohs hardness is ca. 2–3, calculated density is 6.652 g.cm–3. In reflected light, vrančiceite is light grey with a yellowish shade; bireflectance, pleochroism and anisotropy are all weak. Internal reflections were not observed. Reflectance values for the four Commission on Ore Mineralogy wavelengths of vrančiceite in air [Rmax, Rmin (%) (λ in nm)] are: 33.6, 31.2 (470); 33.9, 30.6 (546); 31.1, 30.0 (589); and 32.1, 29.1 (650). The empirical formula, based on electron-microprobe analyses, is Cu10.11(4)Ag0.01(1)Hg2.87(4)Sb0.01(1)Bi0.01(1)S7.99(8). The ideal formula is Cu10Hg3S8 (Z = 2), which requires (in wt.%) Cu 42.54, Hg 40.29 and S 17.17, total 100.00. Vrančiceite is triclinic, P$\bar{1}$, with unit-cell parameters a = 7.9681(2), b = 9.7452(3), c = 10.0710(3) Å, α = 77.759(1), β = 76.990(1), γ = 79.422(1)°, V = 737.01(4) Å3 and Z = 2. The strongest reflections of the calculated powder X-ray diffraction pattern [d, Å (I) hkl] are: 3.354 (76) $\bar{2}$01, 3.111 (68) 222, 2.833 (100) 213, 2.733 (93) 231, 2.705 (76) 2$\bar{2}$1 and 2.647 (71) $\bar{2}\bar{1}$2. According to the single-crystal X-ray diffraction data (R1 = 0.0262), the crystal structure of vrančiceite can be described as comprising Cu–S layers, connected through CuS3 polyhedra, giving rise to a three-dimensional framework with channels running along the a axis and hosting linearly coordinated Hg atoms. Structural relations with gortdrumite are discussed. Vrančiceite is named after its type locality, the Vrančice deposit near Příbram. The mineral and its name have been approved by the Commission on New Minerals, Nomenclature and Classification of the International Mineralogical Association (IMA2022–114).

Vrančiceite 是在捷克共和国波希米亚中部普日布拉姆附近废弃 Vrančice 矿床的旧矿场收集的样本中发现的一种新矿物。弗朗西石以稀有的反角晶粒形式出现，尺寸可达 100 μm，存在于方解石脉石中，与朱砂、朱利石、方铅矿和海地菲石伴生。Vrančiceite 呈黑色，具有金属光泽。莫氏硬度约为. 2-3，计算密度为6.652 g.cm –3。在反射光下，vrančiceite 呈浅灰色并带有淡黄色色调；双反射性、多色性和各向异性都很弱。没有观察到内部反射。空气中钙硅石的四个矿石矿物学委员会波长的反射率值 [ R max、R min (%)（λ in nm）] 为：33.6、31.2 (470)；33.9、30.6（546）；31.1、30.0 (589)；和 32.1、29.1 (650)。基于电子显微镜分析的经验公式为 Cu 10.11(4) Ag 0.01(1) Hg 2.87(4) Sb 0.01(1) Bi 0.01(1) S 7.99(8)。理想的化学式为Cu 10 Hg 3 S 8 ( Z = 2)，需要(以重量％计)Cu 42.54、Hg 40.29 和S 17.17，总计100.00。Vrančiceite 是三斜晶系，P $\bar{1}$，晶胞参数a = 7.9681(2), b = 9.7452(3), c = 10.0710(3) Å, α = 77.759(1), β = 76.990 (1), γ = 79.422(1)°, V = 737.01(4) Å 3且Z = 2。计算得出的粉末 X 射线衍射图 [ d , Å (I) hkl ]的最强反射为： 3.354 ( 76) $\bar{2}$ 01, 3.111 (68) 222, 2.833 (100) 213, 2.733 (93) 231, 2.705 (76) 2 $\bar{2}$ 1 和 2.647 (71) $\bar {2}\bar{1}$ 2. 根据单晶X射线衍射数据（R 1 = 0.0262），氟硅冰石的晶体结构可以描述为由Cu-S层组成，通过CuS 3多面体连接，产生一个三维框架，其通道沿 a轴延伸并容纳线性配位的汞原子。讨论了与硅镁石的结构关系。Vrančiceite 以其典型产地——普日布拉姆附近的 Vrančice 矿床命名。该矿物及其名称已获得国际矿物学协会新矿物、命名和分类委员会 (IMA2022-114) 的批准。