Skip to Main Content
Skip Nav Destination

Edscottite, Fe (sub 5) C (sub 2) , a new iron carbide mineral from the Ni-rich Wedderburn IAB iron meteorite

Chi Ma and Alan E. Rubin
Edscottite, Fe (sub 5) C (sub 2) , a new iron carbide mineral from the Ni-rich Wedderburn IAB iron meteorite
American Mineralogist (September 2019) 104 (9): 1351-1355


Edscottite (IMA 2018-086a), Fe5C2, is a new iron carbide mineral that occurs with low-Ni iron (kamacite), taenite, nickelphosphide (Ni-dominant schreibersite), and minor cohenite in the Wedder-burn iron meteorite, a Ni-rich member of the group IAB complex. The mean chemical composition of edscottite determined by electron probe microanalysis, is (wt%) Fe 87.01, Ni 4.37, Co 0.82, C 7.90, total 100.10, yielding an empirical formula of (Fe4.73Ni0.23Co0.04)C2.00. The end-member formula is Fe5C2. Electron backscatter diffraction shows that edscottite has the C2/c Pd5B2-type structure of the synthetic phase called Haegg-carbide, chi -Fe5C2, which has a = 11.57 Aa, b = 4.57 Aa, c = 5.06 Aa, beta = 97.7 degrees , V = 265.1 Aa3, and Z = 4. The calculated density using the measured composition is 7.62 g/cm3. Like the other two carbides found in iron meteorites, cohenite (Fe3C) and haxonite (Fe23C6), edscottite forms in kamacite, but unlike these two carbides, it forms laths, possibly due to very rapid growth after supersaturation of carbon. Haxonite (which typically forms in carbide-bearing, Ni-rich members of the IAB complex) has not been observed in Wedderburn. Formation of edscottite rather than haxonite may have resulted from a lower C concentration in Wedderburn and hence a lower growth temperature. The new mineral is named in honor of Edward (Ed) R.D. Scott, a pioneering cosmochemist at the University of Hawai'i at Manoa, for his seminal contributions to research on meteorites.

ISSN: 0003-004X
EISSN: 1945-3027
Serial Title: American Mineralogist
Serial Volume: 104
Serial Issue: 9
Title: Edscottite, Fe (sub 5) C (sub 2) , a new iron carbide mineral from the Ni-rich Wedderburn IAB iron meteorite
Affiliation: California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, CA, United States
Pages: 1351-1355
Published: 201909
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 25
Accession Number: 2019-082825
Categories: Mineralogy of non-silicatesPetrology of meteorites and tektites
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 1 table
Secondary Affiliation: University of California Los Angeles, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201944
Close Modal

or Create an Account

Close Modal
Close Modal