Ferraris, Cristiano, Pignatelli, Isabella, Cámara, Fernando, Parodi, Giancarlo, Pont, Sylvain, Schreyer, Martin, Wei, Fengxia (2020) Laurentthomasite,Mg2K(Be2Al)Si12O30: a new milarite-group-type member from the Ihorombe region, Fianarantsoa Province, Madagascar. European Journal of Mineralogy, 32 (3) 355-365 doi:10.5194/ejm-32-355-2020
| Reference Type | Journal (article/letter/editorial) | ||
|---|---|---|---|
| Title | Laurentthomasite,Mg2K(Be2Al)Si12O30: a new milarite-group-type member from the Ihorombe region, Fianarantsoa Province, Madagascar | ||
| Journal | European Journal of Mineralogy | ||
| Authors | Ferraris, Cristiano | Author | |
| Pignatelli, Isabella | Author | ||
| Cámara, Fernando | Author | ||
| Parodi, Giancarlo | Author | ||
| Pont, Sylvain | Author | ||
| Schreyer, Martin | Author | ||
| Wei, Fengxia | Author | ||
| Year | 2020 (June 17) | Volume | 32 |
| Page(s) | 355-365 | Issue | 3 |
| Publisher | Copernicus GmbH | ||
| URL | |||
| Download URL | https://ejm.copernicus.org/articles/32/355/2020/ejm-32-355-2020.pdf+ | ||
| DOI | doi:10.5194/ejm-32-355-2020Search in ResearchGate | ||
| Classification | Not set | LoC | Not set |
| Mindat Ref. ID | 16865360 | Long-form Identifier | mindat:1:5:16865360:9 |
| GUID | d8aad282-2c87-4b55-8731-a0b1ca6ed2db | ||
| Full Reference | Ferraris, Cristiano, Pignatelli, Isabella, Cámara, Fernando, Parodi, Giancarlo, Pont, Sylvain, Schreyer, Martin, Wei, Fengxia (2020) Laurentthomasite,Mg2K(Be2Al)Si12O30: a new milarite-group-type member from the Ihorombe region, Fianarantsoa Province, Madagascar. European Journal of Mineralogy, 32 (3) 355-365 doi:10.5194/ejm-32-355-2020 | ||
| Plain Text | Ferraris, Cristiano, Pignatelli, Isabella, Cámara, Fernando, Parodi, Giancarlo, Pont, Sylvain, Schreyer, Martin, Wei, Fengxia (2020) Laurentthomasite,Mg2K(Be2Al)Si12O30: a new milarite-group-type member from the Ihorombe region, Fianarantsoa Province, Madagascar. European Journal of Mineralogy, 32 (3) 355-365 doi:10.5194/ejm-32-355-2020 | ||
| In | (2020) European Journal of Mineralogy Vol. 32 (3) Schweizerbart | ||
| Abstract/Notes | Laurentthomasite, ideally Mg2K(Be2Al)Si12O30, is a new milarite-group member found within quartz-syenite pegmatites from the Ihorombe region, Fianarantsoa Province, Madagascar. It occurs as euhedral {0001} hexagonal crystals, maximum 15 mm large and 5 mm thick. The crystals show a very strong dichroism with cobalt blue and green-yellow colours when observed along [0001] and [1000], respectively. The mineral is transparent, uniaxial (+) and its lustre is vitreous. The hardness is about 6 (Mohs scale), showing a poor {0001} cleavage, irregular to conchoidal fracture, and a measured density of 2.67(8) g cm−3. Laurentthomasite is hexagonal, space group P6/mcc (no. 192), with a=9.95343(6) Å, c=14.15583(8) Å, V=1214.54(1) Å3 and Z=2. The strongest nine lines in the X-ray powder diffraction pattern [d in Å – (I) – hkl] are 3.171 – (10) – 211, 4.064 – (8) – 112, 2.732 – (8) – 204, 4.965 – (6) – 110, 2.732 – (4) – 204, 3.533 – (3) – 004, 7.055 – (2) – 002, 4.302 – (2) – 200 and 3.675 – (2) – 202. Chemical analyses by electron microprobe and several spectroscopies (inductively coupled plasma, ICP; optical emission, OES; mass, MS; and Mössbauer) give the following empirical formula based on 30 anions per formula unit: (Mg0.86 Sc0.54 Fe0.352+ Mn0.26)∑=2.01(K0.89 Na0.05 Y0.02 Ca0.01 Ba0.01)∑=0.98[(Be2.35 Al0.50 Mg0.11 Fe0.033+)∑=2.99(Si11.90 Al0.10)O30]; the simplified formula is (Mg, Sc)2(K, Na)[(Be, Al, Mg)3(Si, Al)12O30]. The crystal structure was refined to an R index of 1.89 % based on 430 reflections with Io > 2σ(I) collected on a four-circle diffractometer with CuKα radiation. By comparison with the general formula of the milarite group, A2B2C[T(2)3T(1)12O30](H2O) x (0<x<n, with n<2 pfu, per formula unit), the laurentthomasite structure consists of a beryllo-alumino-silicate framework in which the T(1) site is occupied by Si and minor Al and forms [Si12O30] cages linked by the T(2) site mainly occupied by (Be + Al). The A and C sites occur in the interstices of the framework while the B site is vacant. The origin of the strong dichroism is related to a charge transfer process between Fe2+ and Fe3+ in octahedral A sites and tetrahedral T(2) sites, respectively. | ||
Map of Localities
Locality Pages
| Locality | Citation Details |
|---|---|
| Beravina, Ambaro, Tsaraitso, Betroka District, Anosy, Madagascar |
Mineral Pages
| Mineral | Citation Details |
|---|---|
| Laurentthomasite |
Mineral Occurrences
| Locality | Mineral(s) |
|---|---|
| Beravina, Ambaro, Tsaraitso, Betroka District, Anosy, Madagascar | ⓘ Albite, ⓘ Apatite, ⓘ Beryl, ⓘ Cheralite, ⓘ Laurentthomasite, ⓘ Magnetite, ⓘ Orthoclase, ⓘ Pegmatite, ⓘ Phenakite, ⓘ Quartz, ⓘ Thortveitite |
See Also
These are possibly similar items as determined by title/reference text matching only.
