中文摘要：

丁道衡矿-（Ce）：（Ce，La）4Fe^2＋（Ti，Fe^2＋，Mg，Fe^3＋）2Ti2Si4O22，理想的结构化学式Ce2Ce2Fe2＋Ti2Ti2Si4O22，单斜晶系，a=1.34656（15）nm，b=0.57356（6）nm，c=1.10977（12）nm，β=100.636（2）°，V=0.84239（46）nm^3，空间群P21/a（假C2/m），Z=2。作为硅钛铈矿（chevkinite）族矿物的新成员，它产于举世闻名的白云鄂博铁-稀土-铌矿床镁夕卡岩中，多数单晶体长0.2-1.0 cm，最大者长大于1.5 cm。共生矿物有透辉石、透闪石、钠透闪石、褐帘石-（Ce）、磁铁矿、尖晶石、烧绿石、氟金云母、氟磷灰石、石英和萤石等。矿物具有褐色条痕和半金属-金属光泽的黑色，其褐黑色碎片半透明。性脆、具有贝壳状断口、无解理和裂开。显微硬度（VHN25g）为606.0-717.4 kg/mm^2（相当于摩氏硬度约5.9）。矿物实测密度4.83（7）g/cm^3，计算密度值4.88（0）g/cm^3。丁道衡矿-（Ce）的反射色为带灰色的浅黄色，多色性为不同色调的灰色。平均反射率（λ=589nm）为11.4%-12.5%。矿物为二轴晶负光性。作过结构精测的丁道衡矿-（Ce）晶体的电子探针测值：SiO2：19.29，TiO2：18.26，A l2O3：0.04，FeO：8.49，Fe2O3：1.67，ThO2：0.16，MgO：1.32，CaO：2.17，Nb2O5：0.47，Ta2O5：0.00，La2O3：19.53，Ce2O3：28.08，Y2O3：0.00，Na2O：0.01，总量99.46%；其中Fe^3＋/Fe^2＋的比值依穆斯堡尔谱换算。根据结构精测每个单位分子式中O=22和C（1）位上Ti优先占位，计算的矿物晶体化学式为（Ce2.13La1.49Ca0.48Th0.01）Σ4.11Fe2＋（Ti0.88Fe02.＋47Mg0.41Fe03.2＋6A l0.01）Σ2.03（Ti1.96Nb0.04）Σ2.00（Si2O7）2O8。分别用P21/a和C2/m对丁道衡矿-（Ce）的晶体结构作了精测。结果表明，丁道衡矿-（Ce）的真空间群是P21/a。换言之，它才是真正珀硅钛铈矿[perrierite-（Ce）]的同质多象体。显而易见，硅钛铈矿族矿物既可以有P21/a空间群，又可以有C2/m空间群。

英文摘要：

Dingdaohengite-（Ce）, （Ce, La）4Fe^2＋ （Ti, Fe^2＋, Mg, Fe^3＋ ）2Ti2Si4O22, idealy Ce4Fe^2＋ Ti2Ti2 （Si2O7） 2Os, monoclinic, a = 13. 4656 （ 15 ） A, b = 5. 7356 （6） A, c = 11. 0977 （12） A, /3 = 100. 636 （2） ^o, V = 842. 39（46）A3, space-group P21/a （ pseudo- C2/m）, Z =2, is a new member of the chevkinite group minerals from the world-known Bayan Obo REE-Nb-Fe mine in China. The mineral occurs as euhedral or subhedral, short columnar or thick tabular//（001 ） crystals in the magnesian skarn rocks, located mainly in the exocontact between granite and dolomitic marble. Most individual crystals are 0. 2 - 1.0 cm long, the largest one is 〉 1.5 cm in size. Associated minerals are diopside, tremolite, richterite, allanite-（ Ce）, magnetite, ilmenite, spinel, titanite, pyro- chlore, F-rich phlogopite, fluorapatite, quartz, fluorite, etc. The mineral is black with a brown streak and a subme- tallic-metallic luster, translucent in thin fragments being brownish-black in colour. It is brittle with conchoidal frac- tures. No cleavage or parting was observed. Its hardness is VHN25g 606.0 -717.4 kg/mm^2 （Mohs nearly 5.9）. And the measured density is 4. 83 （7） g/cm^3, and the calculated density is 4. 88（0） g/cm^3. In the reflected light, dingdaohengite-（Ce） is yellowish with gray tone, it is pleoehroic with different gray tones, reflectance values （ in the case of）λ =589 nm） are within the range of 11.4% - 12. 5%. It is biaxial negative. Electron-microprobe analysis of the refined structural crystal gave SiO2 19. 29, TiO2 18.26, A1203 0. 04, FeO 8.49, Fe203 1.67, ThO20. 16, MgO 1.32, CaO 2. 17, Nb2O5 0. 47, Ta20s 0. 00, La203 19. 53, Ce203 28.08, Y203 0. 00, Na20 0. 01, and 99. 46 wt% in sum; the Fe^3＋/Fe^2＋ ratio was converted by Mossbauer spectroscopy. The corresponding chemical formula is （Ce2.13La1.49Ca0.48Th0.01）∑4.11Fe^2＋（Ti0.88Fe^2＋0.47Mg0.41Fe0.2^3＋Al0.01）2.03（Ti1.96Nb0.04）∑2.00（Si2O7）2O8,based O=22apfu （ atoms per for