Oxybismutomicrolite, ideally [(Bi3+,#)2]Σ4+Ta2O6O, where # = subordinate substituents, such as Na+, Ca2+ and vacancy (□), is a microlite-group, pyrochlore-supergroup mineral discovered at the Solnechnaya (‘Sunny’) pegmatite vein, Malkhan pegmatite field, Zabaykalskiy Kray, Central Transbaikalia, Russia. It forms rough octahedral crystals up to 1 mm across and equant grains up to 2 mm across embedded in an albite–lepidolite–elbaite complex. Other associated minerals are Bi-rich fluornatromicrolite, bismutotantalite and stibiotantalite. The new mineral is black, with resinous lustre; the streak is greyish white. It is non-fluorescent under ultraviolet light. Oxybismutomicrolite is brittle, with Mohs’ hardness of ~5. Cleavage is not observed, fracture is uneven. Dmeas. = 6.98(2) g/cm3 and Dcalc. = 7.056 g/cm3. The mineral is optically isotropic. The mean refractive index calculated from the Gladstone–Dale equation is 2.184. The infrared spectrum shows the absence of H2O molecules and OH groups. The chemical composition is (electron microprobe, wt.%): Na2O 3.45, CaO 2.88, MnO 0.31, PbO 0.76, Bi2O3 29.81, ThO2 0.18, TiO2 3.89, SnO2 1.77, Nb2O5 4.50, Ta2O5 51.08, F 1.17, O = F –0.49, total 99.31. The empirical formula, on the basis of 2 cations at the B site, is (Bi0.79Na0.68Ca0.32Mn0.03Pb0.02□0.16)Σ2.00(Ta1.42Ti0.30Nb0.21Sn0.07)Σ2.00O6.00(O0.52F0.38□0.10)Σ1.00. The crystal structure refinement (R = 0.019) gave the following data: cubic, Fd–3m, a = 10.4746(11) Å, V = 1149.2(4) Å3 and Z = 8. The eight strongest lines of the powder X-ray diffraction pattern [d, Å(I, %)(hkl)] are: 6.051(12)(111), 3.160(10)(311), 3.026(100)(222), 2.621(32)(400), 1.854(33)(440), 1.581(27)(622), 1.514(7)(444) and 1.203(7)(662). Type material is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, registration number 5409/1.

氧杂弹微晶石，理想地是[（Bi 3+，＃）2 ] Σ4+ Ta 2 O 6 O，其中＃=下级取代基，例如Na +，Ca 2+和空位（□）是在俄罗斯中部Transbaikalia的Zabaykalskiy Kray的Malkhan伟晶岩田Solnechnaya（'Sunny'）伟晶岩脉中发现的微晶群，烧绿石-超群矿物质。它形成钠长石-锂云母-钠长石复合物，嵌入的粗八面体晶体最大可达1毫米，等效晶粒最大可达2毫米。其他相关矿物是富含Bi的萤石微晶石，双钽钽矿和stitantantalite。新矿物为黑色，具有树脂光泽。条纹为灰白色。在紫外线下不发荧光。氧比微晶石易碎，莫氏硬度约为5。没有观察到卵裂，断裂不均匀。D测量。= 6.98（2）g / cm 3和D钙。= 7.056克/厘米3。矿物是光学各向同性的。根据Gladstone-Dale方程计算得出的平均折射率为2.184。红外光谱显示不存在H 2 O分子和OH基团。化学成分为（电子探针，wt。％）：Na 2 O 3.45，CaO 2.88，MnO 0.31，PbO 0.76，Bi 2 O 3 29.81，ThO 2 0.18，TiO 2 3.89，SnO 2 1.77，Nb 2 O 5 4.50 ，Ta 2 O 5 51.08，F 1.17，O = F –0.49，总计99.31。基于B处的两个阳离子的经验公式为（Bi 0.79 Na 0.68 Ca0.32锰0.03铅0.02 □ 0.16）Σ2.00（TA 1.42的Ti 0.30 Nb的0.21的Sn 0.07）Σ2.00 Ô 6.00（O 0.52 ˚F 0.38 □ 0.10）Σ1.00。晶体结构细化（[R = 0.019），得到以下数据：立方体，FD- 3米，一个= 10.4746（11）A，V = 1149.2（4）3和Ž = 8。8条最强粉末X线射线衍射图d，Å（I，％）（hkl）]为：6.051（12）（111），3.160（10）（311），3.026（100）（222），2.621（32）（400），1.854（33） （440），1.581（27）（622），1.514（7）（444）和1.203（7）（662）。字体材料存放在俄罗斯莫斯科俄罗斯科学院菲斯曼矿物学博物馆的藏品中，注册号5409/1。