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An Ungrouped Iron - Elton |
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| Meteorite, Elton, Iron, ungrouped |
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| Figure 1. Scale bar 700 µm. |
| Images, Elton iron meteorite |
| The Elton iron meteorite, partially recrystallized kamacite, distorted Neumann lines (plus cross-hatched), partially visible Widmanstatten lamellae, and schreibersite. Note: The kamacite Vickers microhardness of this sample was measured at 280 +/- 15. |
| Classification systems exist to sort
materials, chemistry, stars, mineralogy, etc., into like-kinds. It is similar within meteoritics. With over 74,000 known registered meteorites, classification systems provide baselines of chemistry and mineralogy for sorting new Finds or Falls. For the 1,300+ iron meteorites known, there are currently 13 chemical classification groups. One hundred fifty-two of the 1,300 do not fit into these groups. These ungrouped iron's unique compositions likely arise from their distinct origins. They may have originated from small, isolated parent bodies that experienced different formative processes. Some may have experienced severe shock metamorphism from high-velocity impacts causing rapid heating, melting, recrystallization, Neumann bands, and more. Others may reflect variations in the initial composition of their parent bodies or formed in regions with unique chemical conditions or properties. Ungrouped irons are diverse in their chemical composition and structure. Some of this structural diversity can be seen in the images listed in the catalog topics - Tishomingo, Tucson Ring, Redfields, Ysleta, Commanche, Nordheim, Gebel Kamil, Elton, and Cowra, each unique in its own right. |
| Elton Little has been published on this iron. A scholarly document search returns an Elbert A. King, University of Houston, TX, abstract, a brief Buchwald (1975) metallographic observation of troilite-schreibersite rosettes, a trace element chemistry suggesting Elton is related to IIB irons, and a Buchwald (1975) entry in the "Handbook of Iron Meteorites" citing a personal communication with Wasson (1970) on Elton's chemistry. High-resolution metallographic imagery was not found. The following is a synopsis of these three abstracts, followed by high-resolution imagery from prepared surfaces of the Elton iron (note, only abstracts were published): "The Elton, Texas iron was recovered from a cultivated field on the farm of Mr. E. T. Varnell, approximately 8 km E-NE of the Elton Post Office, in Dickens County, Texas, in 1936 or 1937. Mr. Varnell had noticed the object in his field as early as 1935 or 1936, but he did not bring the object into his house until approximately one year later." "The Elton meteorite probably is the same as the fall that occurred in the area accompanied by a hissing or frying sound early in the summer of 1933. The specimen was recognized as a meteorite by Mr. Glen Evans of the University of Texas, Bureau of Economic Geology in April, 1938." "The initial weight was approximately 1.973 kg, the surface only slightly weathered, and the specimen is listed as "probably a medium octahedrite" in Barnes (1939) Catalog of Texas Meteorites based upon an examination of a small "ground" surface." King, (1975) later noted, "A new surface examination revealed that the iron is a medium to coarse octahedrite with kamacite lamellae ranging from 0.5 to more than 1.5 mm. Chemical analysis of the "metal" by Jun Ito gave the following in weight percent: Fe 91.6, Ni 6.9, Co 0.34, O 0.36, Cr 0.01, Cu 0.01, C 0.01, and trace S." He also noted, "Two troilite inclusions, greater than 1 cm in diameter, swathing kamacite parallel to the margins of the troilite, and abundant schreibersite." |
| Figure 2. Scale bar 1.3 mm. |
| Elton, altered structures. Partially recrystallized kamacite (left). Net plessite field nucleated with taenite (center). |
| Figure 3. Scale bar 1 mm. |
| Altered comb and net plessite field, center. Oriented skeleton schreibersite crystal, right. |
| Figure 4. Scale bar 80 µm |
| Net plessite field nucleated with taenite grains. |
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