Rare meteorite fragment or worthless earth rock?
inApril 9, 2013 - 1:08pm
The explosion of a meteor near Chelyabinsk, Russia on February 15, 2013 Russia, created more than sensational disaster headlines in worldwide media.
Almost immediately a gold rush-style craze set in as former commune Communists quickly became aware of the international market for meteorite fragments. Relatively small authenticated meteor fragments can sell for hundreds to thousands of dollars depending on various characteristics.
Fragments purporting to be from the Chelyabinsk meteor began appearing on internet auction sites such as eBay within days. By February 19, 2013, many of these fragments were ending at prices from $200 to $1000. Since then, fragments attributed to the Chelyabinsk event have continued to be posted with pieces frequently selling for over $1000.
So are all these pieces authentic? And does the average person—not a dedicated space rock collector or geologist—even know what properties an authentic meteorite fragment should possess?
The first step to understanding the nature of such fragments is to discuss the basic terminology. A meteor is the flaming tail or bright streak of light produced by a meteoroid. The tail is produced from friction between the fast moving meteoroid and the earth’s atmosphere. Stone-like fragments created from a burning meteoroid that fall to earth are meteorites.
For collectors—for which a general non-academic discussion is probably adequate—there are basically two broad categories of meteorites: those made primarily of iron with various amounts of other metal and those composed of stone. About ten per cent of all meteorites are iron based; the remaining approximately ninety per cent are stone. The rarest meteorites are from the planet Mars thought to have been set adrift by asteroid strikes and eventually drifting into Earth’s orbit.
Amateur collectors generally find iron meteorites the easiest to identify because of their attraction to a magnet. They are also easier to find than other types of meteorites because they can be located by dragging a large magnet over the ground or using a metal detector. Relatively large areas can be searched fairly quickly using either method. Metal detectors have the added advantage of being able to locate pieces hidden below the surface and in rough terrain covered with debris or vegetation. Be careful, though, not to use magnetic attraction as your only test. Any common terrestrial rock with iron ore present will also be attracted to a magnet.
Stone meteorites are generally much harder to find because they so closely resemble ordinary terrestrial stone and rocks. One of the visual characteristics that help identify authentic stone meteorites is a thin black cinder- or charred-like coating on their surface known as a fusion crust. The fusion crust is formed by heat and burning as the meteorite passes through the friction of the earth’s atmosphere. While a fusion crust originally formed on virtually all stone meteorites, it may or not be present or fully intact when found. The crust is subject to wearing off if the meteorite is exposed to severe weathering, wind or fluid tumbling. A stone meteorite which breaks or cracks after the initial fusion crust formed will also lack crust on the face of the broken surfaces.
According to information posted on a meteorite collector's site, Meteorite-Identification.com, less than one in a thousand samples which are scientifically tested are true meteorites. If you’re just getting interested in meteorites, be sure you understand what is being sold. Request the seller provide a guarantee a piece is genuine and what the refund policy is if the piece is determined not to be authentic.
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by Mark Chervenka