While it need to be stated that techniques for obtaining fine detail in micro etching for research purposes can be done efficiently using nitric acid, there are alternatives that are attractive to collectors who want a simple but efficient method to etch meteorites for display use.Ī number of years ago, my son, Jim, began experimenting with a commercial product packaged for Radio Shack (an American electronics’ chain which caters to hobbyists) which is solid as a circuit board etchant. Perry, (1944), in discussing etching reagents cites the usefulness of ferric chloride in etching meteorites as “minor”.
#Iron meteorite how to#
As early as 1915, Farrington, and later Nininger, (1936) taught us how to etch an iron meteorite using nitric acid. In meteorite circles we have all grown up to believe in nitric acid as the favored (and presumably only) choice. (Dowdell,) Three of these that are well known in industry are nitric acid (nital), hydrochloric acid, and ferric chloride. There are, in fact, many industrial etchants, all having specific uses. The patterns we see in meteorites, however, are unique and characteristic. Iron alloys will etch because as they cool their different metal components (phases) will freeze out at various temperatures, forming characteristic crystalline arrangements. The angles formed by the bands is dependent on how the meteorite is cut.Įtching patterns are not unique to meteorites. (The details of how all this comes about is a fascinating study and will be discussed next month.) Kamacite (the wider bands) is more easily dissolved than taenite by acid and thus the plate structure is revealed upon etching. The fields between the bands is a mix of kamacite and taenite (a supersaturated solution of taenite and kamacite) called plessite. This results in differences in crystallization during the cooling process. Taenite has a higher percentage of nickel, having solidified from a solid solution of iron and nickel at a higher temperature than kamacite. It is during this period of cooling that the kamacite separates from taenite. (The iron has already become a solid but is not yet rigid. Silicated Campo del Cielo Iron (ferric chloride-etched by Jim Hartman)Ī nickel-iron meteorite having an octahedral crystalline structure is essentially an alloy of consisting of two phases of nickel-iron, kamacite and taenite.
#Iron meteorite series#
Fifth in a series of introductory topics for the beginning meteorite collector! 205 g.
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