Osmium (element)
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Osmium is named after the Greek word όσμη meaning odor, for it's pungent and irritating odor when heated in air.

Discovered in 1804; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Os,Ir,Ru)

Osmium, Iridium, Ruthenium

Molecular Weight:

190.71 gm

Composition:

Iridium

25.20 %

Ir

Osmium

74.80 %

Os

100.00 %

Classification

Mineral Classification:

Elements

Strunz 8th Ed. ID:

1/A.13-20

Nickel-Strunz 10th Ed. ID:

1.AF.05

1 : ELEMENTS (Metals and intermetallic alloys; metalloids and nonmetals; carbides, silicides, nitrides, phosphides)
A : Metals and Intermetallic Alloys
F : Platinum group elements

Related to:

Platinum Group Elements.

Members of Group:

Platinum Group Elements: Platinum, Osmium, Iridium, Ruthenium, Rhodium, Palladium

Varieties:

Iridosmine, Rhodic Nevyanskite

Synonyms:

ICSD 40323, Iridosmine, Nevyanakite, PDF 41-601, Rutheniridosmium, Siserskite

Crystal Data

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

Physical Properties

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

Optical Properties

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

Occurances

Geological Setting:

With other platinum-group elements and alloys, in ultramafic rocks and placers derived therefrom.

Common Associations:

Rutheniridosmine, Iridosmine, Osmiridium (Ruby Creek, Canada); Bowieite, Platinum, Ir–Pt alloys, Laurite, silicate inclusions (Salmon River, Alaska, USA); Isoferroplatinum, Cuprorhodsite, Malanite, Cuproiridsite, Iridosmine, Laurite, Erlichmanite, Cooperite, Sperrylite, Chalcopyrite, Bornite (Russia).

Common Impurities:

Pt, Rh, Pd

Type Locality:

Urals Region, Sverdlovskaya Oblast', Nizhnii Tagi, Russia

Year Discovered:

1804

View mineral photos:

Osmium Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

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 literature as the "PGE's". Osmium is named after the Greek word όσμη meaning odor, for it's pungent and irritating odor 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 luster 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 Pilpe, Colombia. In the Santiago River placers, Esmeraldas Province, Ecuador. In Russia, in the 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.
 

  
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