Osmium
Osmium is a member of the Platinum Group elements that includes Platinum, Osmium, Iridium, Ruthenium, Rhodium and Palladium. The Platinum Group elements often occur in native form, often together and often alloyed with each other. They are frequently referred to in the literature as the “PGE’s”. Osmium is named after the Greek word όσμη meaning odour, for it’s pungent and irritating odour when heated in air.
Osmium is unique in several ways. It is the least abundant stable element in the Earth’s crust. It is the densest naturally occurring element, with a density of 22.59 g/cm3. It has the fourth highest melting point of all elements, with a melting point of 3306 K (3033°C, 5491°F). It has a relatively high Moh’s hardness of 6 – 7. Osmium is hard but brittle and maintains its high metallic lustre even at high temperatures. Because of its very high density, very high melting point and high hardness, solid Osmium is difficult to machine, form or work.
Osmium distribution: from Ruby Creek, Atlin, British Columbia, Canada. In the USA, at Fox Gulch and the Salmon River, Goodnews Bay, Alaska. From Rio Pipe, Colombia. In the Santiago River placers, Esmeraldas Province, Ecuador. In Russia, in the Gusevogorskii pluton, and the Kytlym and Uktus complexes, Ural Mountains; from the Neozhidannyy Creek placers, Tuva; and in the Pustaya River placers, Kamchatka Peninsula. At the Harold’s Grave and Cliff quarries, Baltasound-Haroldswick area, Unst, Shetland, Scotland. In Ethiopia, in the Joubdo stream, on the Birbir river. From the Witwatersrand, Transvaal, South Africa. At Anduo, Tibet, China. From the Sorashigawa placers, ?? Prefecture, Japan. Additional minor localities are known.
| Chemical Formula: | (Os, Ir, Ru) |
| Osmium, Iridium, Ruthenium | |
| Molecular Weight: | 190.71 gm |
| Composition: | Iridium | 25.20 % | Ir | ||
| Osmium | 74.80 % | Os | |||
| 100.00 % |
| Crystallography: | Hexagonal – Dihexagonal Dipyramidal |
| Crystal Habit: | Rare crystals are hexagonal tabular, to 3 mm; commonly as euhedral prismatic inclusions in Pt–Fe alloys. |
| Twinning: | None |
| Cleavage: | Perfect on {0001} |
| Fracture: | Elastic; fragments spring back after bending |
| Tenacity: | Brittle |
| Moh’s Hardness: | 6.0 – 7.0; Vickers: VHN25=1206 – 1246 kg/mm2 |
| Density: | 22.48 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | White, with a bluish gray tinge in reflected light |
| Transparency: | Opaque |
| Luster: | Metallic |
| Refractive Index: | R1–R2: (400) — , (420) 62.7–63.9, (440) 63.9–64.7, (460) 63.9–64.6, (480) 63.8–64.4, (500) 63.3–63.8, (520) 62.7–63.2, (540) 62.1–62.7, (560) 61.5–61.8, (580) 60.9–61.4, (600) 60.4–60.7, (620) 59.9–60.2, (640) 59.6–59.8, (660) 59.3–59.9, (680) 59.2–60.0, (700) 59.4–60.0 |
| Birefringence: | 0.000 (opaque) |
| Dispersion: | n/a |
| Pleochroism: | Noticeable to weak |
| Anisotropism: | Strong; reddish orange |
