新矿物──铊明矾

A NEW MINERAL-LANMUCHANGITE

铊明矾 (lanmuchangite ,TlAl[SO4]2 ·12H2 O)是在贵州滥木厂铊 (汞 )矿床富铊矿体氧化带中发现的一种铊的硫酸盐新矿物。该矿物为产于氧化带的次生矿物 ,其共生矿物为水绿矾、镁铝矾、钾明矾、黄钾铁矾、石膏、自然硫、砷华及某些未知矿物。其矿物集合体大小一般为 2～ 10mm ,集合体多为致密块状 ,单晶呈他形粒状 ,4 0～ 90 μm ,偶见平行柱状集合体 ,半自形至自形柱状晶体 ,直径 15～ 65 μm。白色至淡黄色 ,玻璃光泽 ,透明 ,易溶于水。偏光显微镜下无色 ,均质体 ,实测折光率为 1.4 95。维氏硬度为 94～ 12 4kg/mm2 ,摩氏硬度为 3 .1～ 3 .4 ,实测密度 2 .2 2 g/cm3。平均化学成分 :Tl2 O =3 3 .2 5 % ,Al2 O3=8.0 7% ,SO3=2 5 .19% ,SiO2=0 .10 % ,K2 O =0 .3 5 % ,CaO =0 .0 8% ,MgO =0 .0 6% ,FeO =0 .0 4 % ,H2 O =3 3 .4 6% ,总和 10 0 .60 % ,除结晶水由热重分析 (TG)求得 ( 3件样品平均 )外 ,其余成分均由电子探针分析 ( 6点平均 )求得。化学式为(Tl1.0 0 K0 .0 5) 1.0 5(Al1.0 1Si0 .0 2 Ca0 .0 1Mg0 .0 1Fe0 .0 1) 1.0 6 [SO4]2 .0 2 ·11.86H2 O ,理论式为TlAl[SO4]2 ·12H2 O。X射线粉末衍射主要强线 [d(I,hkl) ]为 :0 .4 3 14 ( 10 0 ,2 2 0 ) ,0 .2 80 1( 70 ,3 3 1) ,0 .70 3 ( 5 4 。

Thallium hydrous sulphate is a new mineral. It was discovered in the oxidation zone of Tl-rich ore bodies, Lanmuchang Tl (Hg) deposit, Xinren County, Guizhou Province and is associated with melanterite, pickeringite, potassium alum, jarosite, gypsum, arsenic blane, sulphur and some unknown minerals. The aggregates of lanmuchangite ranging from 2 to 10 mm in size. In general, they consist of anhedral granular crystals ranging from 40 to 90 μm in size, but the boundary is not clear. Occasionally the mineral aggregates occur in parallel columnar form and they consist of subhedral to euhedral columnar crystals ranging from 15 to 65μm in diameter. White, light yellow to white, glassy luster, and transparent. Under the polarization microscope: colorless, homogeneous, N meas. = 1.495 . The mineral is water-soluble. Hv meas. =94～124 kg/mm 2, Hm=3.1～3.4. D meas. = 2.22 g/cm 3. The average composition is: Tl 2O=33.25, Al 2O 3=8.07, SO 3=25.19, SiO 2=0.10, Na 2O=0.00, K 2O=0.35, CaO=0.08, MgO=0.06, FeO=0.04, H 2O=33.46% [In addition to crystal water (H 2O) measured by thermogravimetery (TG), the other constituents determined by electron microprobe], totaling 100.60 wt%. The empirical formula is (Tl 1.00 K 0.05 ) 1.05 (Al 1.01 Si 0.02 Ca 0.01 Mg 0.01 Fe 0.01 ) 1.06 2.02 ·11.86H 2O; the simplified formula is TlAl 2·12H 2O. The strongest diffraction lines d(I, hkl)] from the X-ray power diffraction data are 0.431 4 (100, 220), 0.2801 (70,331), 0.703 (54,111), 0.273 1 (35,420), 0.611 (27,200), 0.352 4 (24,222), 0.367 6 (22,311), 0.305 1 (22,400), 0.235 0 (21,511), 0.326 3 (20,321), 0.249 4 (20,422), 0.193 2 (19,620) nm. Lanmuchangite is of isometric system, space group Pa3, with a=1.221 2(5) nm, V= 1.821 (2) nm 3, and Z=4, compatibility=1-Kp/Kc=-0.032. So it is excellent. The TG curve showed that crystal water was lost (i.e., dewatered) at the 101,135 and 230 ℃; until 243 ℃ dewatering process finished when the loss of crystal water reached up to 33.30%. IR spectroscopic analyses showed the absorption bands at 3 374～3 147 and 1 655～1 648 cm -1 occurred since tensible and bending vibration of crystal water molecules (H 2O) whereas the absorption bands at 1 131 and 605 cm -1 occurred starting from tensible and bending vibration of group 2- . The mineral lanmuchangite is named after the locality where it was discovered. In June of 2001, the mineral and its name officially were approved by the IMA-CNMMN. The typical material is deposited at the Geological Museum of China, Beijing.