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March 04, 2000 at 16:40:53
I have noticed a few posts with questions about meteorites. There are three major groups of meteorites. Stoneys, which are made up of almost entirely stony material. Stoney-irons, which are a mix of iron(w/nickel)and stoney material. And of course, irons, which are almost completely iron with the exception of as much as 20% nickel thrown into the mix.
Irons are fairly easy to recognize in the field. They are the most common type of meteorite found by T/H's(for obvious reasons). When a rock enters our atmosphere at over 20 km per second(thats right) it could be compared to launching a watermelon underwater at a couple of hundred miles per hour. The sheer force of the friction will blow its way right through the rhine and out the rear end. The same happens to a meteor when it enters the atmosphere. Suddenly it encounters friction which begins to incinerate its exterior. This incineration is refered to as "ablation". Irons tend to develop pits or "thumbprints" when ablating. Especially if they are not tumbling too aggressively. The ablated surface hardens as the meteorite slows from the friction. This surface is known as the "fusion crust" and may range in color(for irons) from black(fresh fall) to brown, red, or rust, depending on the age and location of the find. Often the friction will slow the meteorite to terminal velocity if it had not burned up entirely. At this point you will no longer see the streak in the sky. If you are fortunate, you will see the meteorite fall as if it were a regular rock. This event has only been witnesses a few times in world history.
Stony irons are a bit harder to recognize in the field. Most people who hunt for meteorites using metal detectors prefer the gold specific machines. Gold is often found in a matrix with quartz or some other type of stoney material. If your detector tunes out "hot rocks", then you will probably not find any stoney irons unless the iron content is high, which in many cases it is. Stoney-iron meteorites ablate the same as all others but have a tendacy to not show deep regmaglypts(thumbprints). That is not always the case however.
Lastly, stoney meteorites. These type of meteorite are most abundant yet are hardest to find. They often will look like regular rocks. The fusion crust can be one of many natural earth colors, brown, black, gray, tan, redish, etc. It is doubtful that you will detect a stoney. Although there is a lmost always some percentage of iron in them.
I use a Whites Goldmaster III for meteorite hunting. So far, my smallest target was 1/2 of a rusted needle two inches underground(sand). My deepest was a few inches shy of three feet! We had two shovels going at once on a beach in northern Michigan just to discover a piece of concrete that had some re-rod in it. Wow!! I admit, we reburied that one. I use the 14 inch Sierra Gold Max coil with my GM3. It helps me find large targets that are deep. Perfect for meteorites!
Meteorite value ranges from $.25 a gram to $100 a gram in most cases. Irons are the least desirable. An oriented specimen(no tumbling through atmosphere, deeper and directional regmaglypts) can fetch a better price. Stoney-irons and stoneys are more desirable. But if you are real lucky, you may just find a mars rock or a lunar rock. Potentially worth hundreds of thousands to millions. But you have to know where the buyers are.
If you think that you have found a meteorite drop me an email and a pic if you can. I would be happy to help you determine if in fact you have.
Happy Hunting,
George Nicula
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