Okruginite, Cu2SnSe3 is a new mineral discovered from the high-sulfidation epithermal Au Ozernovskoye deposit, Kamchatka peninsula, Russia. It occurs as distinct Se-rich zones in Se-bearing mohite crystals or forms aggregates of small crystals 10–15 μm in size in quartz. In plane-polarised light, okruginite appears brownish grey. Pleochroism and bireflectance are discernible, anisotropy is weak, with rotation tints pale blue-grey to pale grey-brown; it exhibits no internal reflections. Reflectance values of the synthetic analogue of okruginite in air (R1, R2 in %) are: 25.9, 26.5 at 470 nm, 27.5, 26.5 at 546 nm, 27.8, 28.4 at 589 nm and 27.7, 28.4 at 650 nm. Twenty seven electron-microprobe analyses of okruginite give an average composition: Cu 29.48, Sn 28.10, Se 33.40 and S 8.75, total 99.73 wt.%, corresponding to the empirical formula Cu1.99Sn1.02(Se1.82S1.17)Σ2.99 based on 6 atoms; the average of seven analyses on its synthetic analogue is: Cu 23.62, Sn 24.37 and Se 49.09, total 97.08 wt.%, corresponding to Cu1.86Sn1.03Se3.11. The density, calculated on the basis of the empirical formula, is 5.126 g/cm3. The mineral is monoclinic, space group Cc, with a = 6.9906(2), b = 12.0712(4) Å, c = 6.9723(2) Å, β = 109.350(10)°, V = 555.1(2) Å3 and Z = 4. The crystal structure was solved and refined from the powder X-ray-diffraction data of synthetic Cu2SnSe3. Okruginite is the selenium-end member of the Cu2SnS3–Cu2SnSe3 solid solution. The mineral name is in honour of Dr. Victor Mikhailovich Okrugin, a Russian mineralogist, for his contributions to mineralogy and geology of epithermal deposits, in particular of the Au–Ag deposits in Kamchatka.

Okruginite，Cu 2 SnSe 3是在俄罗斯堪察加半岛高硫化浅成热液 Au Ozernovskoye 矿床中发现的一种新矿物。它在含硒莫伊石晶体中以明显的富硒区域出现，或者在石英中形成尺寸为 10-15 μm 的小晶体聚集体。在平面偏振光下，奥鲁长岩呈棕灰色。多色性和双反射性明显，各向异性较弱，旋转色调为浅蓝灰色至浅灰棕色；它没有表现出内部反射。绿晶石的合成类似物在空气中的反射率值（R 1、R 2以%计）为：470 nm处25.9、26.5，546 nm处27.5、26.5，589 nm处27.8、28.4以及650 nm处27.7、28.4。对 okruginite 的 27 次电子微探针分析得出平均成分：Cu 29.48、Sn 28.10、Se 33.40 和 S 8.75，总计 99.73 wt.%，对应于基于经验式 Cu 1.99 Sn 1.02 ( Se 1.82 S 1.17 ) Σ2.99 6 个原子；其合成类似物七次分析的平均值为：Cu 23.62、Sn 24.37 和 Se 49.09，总计 97.08 wt.%，对应于 Cu 1.86 Sn 1.03 Se 3.11。根据经验公式计算的密度为5.126g/cm 3。该矿物为单斜晶系，空间群Cc，a = 6.9906(2)、b = 12.0712(4) Å、c = 6.9723(2) Å、β = 109.350(10)°、V = 555.1(2) Å 3和Z = 4。根据合成Cu 2 SnSe 3的粉末X射线衍射数据解析并细化晶体结构。Okruginite是Cu 2 SnS 3 –Cu 2 SnSe 3固溶体的硒端成员。该矿物名称是为了纪念俄罗斯矿物学家 Victor Mikhailovich Okrugin 博士对浅成热液矿床（特别是堪察加金银矿床）的矿物学和地质学的贡献。