Yarlongite: A New Metallic Carbide Mineral

Yarlongite occurs in ophiolitic chromitite at the Luobusha mine (29°5′N 92°5′E, about 200 km ESE of Lhasa), Qusum County, Shannan Prefecture, Tibet Autonomous Region, People's Republic of China. Associated minerals are: diamond, moissanite, wüstite, iridium (“osmiridium”), osmium (“iridosmine”), periclase, chromite, native iron, native nickel, native chromium, forsterite, Cr‐rich diopside, intermetallic compounds Ni‐Fe‐Cr, Ni‐Cr, Cr‐C, etc. Yarlongite and its associated minerals were handpicked from a large heavy mineral sample of chromitite. The metallic carbides associated with yarlongite are cohenite, tongbaite, khamrabaevite and qusongite (IMA2007–034). Yarlongite occurs as irregular grains, with a size between 0.02 and 0.06 mm, steel‐grey colour, H Mohs: 5½–6. Tenacity: brittle. Cleavage: {0 0 1} perfect. Fracture: conchoidal. Chemical formula: (Cr₄Fe₄Ni)_Σ9C₄, or (Cr,Fe,Ni)_Σ9C₄, Crystal system: Hexagonal, Space Group: P6₃/mc, a= 18.839(2) Å, c= 4.4960 (9) Å, V= 745.7(2) ų, Z= 6, Density (calc.) = 7.19 g/cm³ (with simplified formula). Yarlongite has been approved as a new mineral by the CNMNC (IMA2007–035). Holotype material is deposited at the Geological Museum of China (No. M11650).