![]() Rusting– This isn’t one I thought about including until I came across a YouTube video where a guy said that the presence of rust spots was a sure fire sign of a meteorite.For a great explanation on meteorites and magnetism, along with the best advice I’ve seen concerning the subject, click here. These are nearly indistinguishable from earth basalt unless you plan on doing an oxygen isotope analysis. However, meteorites that come from the moon and Mars are not magnetic. The more iron-nickel you have in a rock, the more attracted it is to a magnet. Magnetism– This is shared by both space and earth rocks alike, making it a tricky diagnostic tool.Now, let’s talk about the not-so-exclusive qualities of a stony meteorite The same caveat applies with these as well: weathering can sneak in through surface cracks and eat away at chondrules and leave behind the vague outline of relict chondrules.Īn iron meteorite showing large thumb prints, or regmaglypts, on its surface (Image from Wikipedia) They’re not always visible in a hand sample, but if you see them with hand lens, you have a meteorite. No earth rock comes close to mimicking the appearance of these little spherical inclusions. Chondrules– I would say that these are the definitive characteristic of a meteorite.Just know that terrestrial rocks will not have a fusion crust. It can weather away if left to the mercy of earth’s climate for too long. One caveat though: not all meteorites will retain their fusion crust. If you see a rock with this characteristic you’ve got a meteorite. It’s also common to see a matte surface instead of a glossy one. The exterior starts to melt from the friction generated heat, and if the meteor is large enough to survive its bumpy ride, instantly cools to form a glassy, black surface. Fusion crust– This is the shiny black surface that forms on a meteor as it rockets through the earths atmosphere.So, let’s get into the first two definitive characteristics: Iron meteorites are obvious, so I won’t delve into those. These guidelines are only valid for stony meteorites. There is some leeway because meteorites are from the same material which the earth formed. With two exceptions, most of the differentiating criteria for meteorite identification are not set in stone (sorry… I couldn’t resist the pun). There are a few characteristics to look for when determining if you’ve found a meteorite. It actually makes for a great teaching moment. So, in no way am I denigrating those that hunt the space rock that I may end up studying. He was obviously passionate about his hunt as displayed by the number of locations he had visited during his meteorite search. To be fair, finding meteorites isn’t easy regardless of what it may look like on T.V. They all displayed the smooth contours that typify rocks of a fluvial environment. Instead he had some really nice river rocks. Unfortunately, the gentleman didn’t find a single meteorite. He obviously went to a lot of effort to collect these rocks and he was wanting us to tell him if any were meteorites. On these cards he noted where the samples came from, when they were collected, and most importantly, his assumption of what type of meteorite he found. In this box were about four large ziploc bags, each loaded with rocks that were cataloged on 3×9 index cards. Last summer, when I did my first project with the meteorite lab, a gentleman had dropped of a box full of rocks.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |