Rossmanite
Rossmanite is a relatively new Tourmaline species that was discovered in 1996 near Rožná, western Moravia, Czech Republic. It is named after George R. Rossman (1944 – ), California Institute of Technology, Pasadena, California, USA, in recognition for his work on the spectroscopy of the tourmaline-group minerals and many other mineral species. Rossmanite forms pink euhedral columnar crystals about 25 mm long and 5 mm thick. It is indistinguishable from the Rubellite variety of Elbaite that it often occurs with and requires identification by quantitative chemical analysis. One of the proven finds of Rossmanite occurs at the Tanco Mine, Bernic Lake, Lac-du-Bonnet area, Manitoba, Canada. The cabochon pictured above is from the Tanco Mine.
Locations for Rossmanite: the type locality at Rožná pegmatite (Rozna; Roschna), Žďár nad Sázavou, Vysočina Region, Moravia (Mähren; Maehren), Czech Republic. In Canada at the Tanco Mine, Bernic Lake, Lac-du-Bonnet area, Manitoba. In Italy at the Grotta d’Oggi Quarry, San Piero in Campo, Campo nell’Elba, Elba Island, Livorno Province, Tuscany. In the UK at the Dorothy China Clay Pit, Whitemoor, St Stephen-in-Brannel, St Austell District, Cornwall, England. Other minor localities also exist including in China, Germany, the Republic of Congo, Russia, Sweden, Tanzania, the United States, Vietnam, Madagascar, Mozambique, Namibia and Nigeria.
| Chemical Formula: | [](LiAl2)Al6(Si6O18)(BO3)3(OH)4 |
| Vacancy-dominant Lithium Aluminum Boro-Silicate Hydroxide | |
| Molecular Weight: | 923.75 gm |
| Composition: | Lithium | 0.75 % | Li | 1.62 % | Li2O |
| Aluminum | 23.37 % | Al | 44.15 % | Al2O3 | |
| Silicon | 18.24 % | Si | 39.03 % | SiO2 | |
| Boron | 3.51 % | B | 11.30 % | B2O3 | |
| Hydrogen | 0.44 % | H | 3.90 % | H2O | |
| Oxygen | 53.69 % | O | |||
| 100.00 % | 100.00 % | = TOTAL OXIDE |
| Crystallography: | Trigonal – Ditrigonal Pyramidal |
| Crystal Habit: | Euhedral columnar crystals about 25 mm long and 5 mm thick, elongated along the c axis with striations parallel to c on the prism faces. |
| Twinning: | None |
| Cleavage: | None |
| Fracture: | n/a |
| Tenacity: | Brittle |
| Moh’s Hardness: | 7.0 |
| Density: | 3.00 – 3.06 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Pink, pale-pink to colorless; colorless in thin slivers and in transmitted light |
| Transparency: | Opaque |
| Luster: | Vitreous |
| Refractive Index: | 1.624 – 1.645 Uniaxial ( – ) |
| Birefringence: | 0.021 |
| Dispersion: | n/a |
| Pleochroism: | n/a |
