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Help with potential meterorite identification

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#1 quietlifeboy

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Posted 13 March 2016 - 08:09 PM

I found several magnetic rocks in central Texas this weekend which I reckon are probably magnetite but I am a super newbie to this sort of thing and hoped I could get some further insight from more knowledgeable individuals. I filed down one of them and that revealed a lighter metallic colour underneath with a vague pattern but it is hard to make out. Unfortunately my camera doesn't take great macro shots but the images of what I found are here-

http://imgur.com/a/dlBGI

 

Thanks!



#2 Stargezzer

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Posted 13 March 2016 - 08:53 PM

There are some id keys online that you can use. If I remember correctly the final determination is the color the rock leaves on a scratch plate. It's all in the instructions. It's highly probable it's magnetite.


Good luck

George

#3 quietlifeboy

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Posted 13 March 2016 - 10:37 PM

Thanks. I've gone through all the online advice I can find and am still unsure. I've rubbed some on paper and some stainless steel and got no marks from the paper and just a colourless scratch on the steel. I will investigate further!



#4 North of Sixty

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Posted 14 March 2016 - 01:17 AM

You can use a unglazed piece of porcelain tile for a 'streak plate' to check for streak. I've often used a piece of broken porcelain from an old kitchen sink. If you can sacrifice a piece of your find, wrap it in some old canvas and smash it up a bit with a hammer and then use a small shallow bowl as a mini-gold pan and swish it around to separate the mineral grains by specific gravity. Then try using your magnet and see what sticks and what doesn't. Use a piece of plastic wrap on the magnet to keep the grains from sticking to the magnet. Any metallic grains should flatten and bend like metal rather than shatter like most minerals do. If you have a hand lens or magnifying glass you can check the grains to see if they break along crystal planes or not as well as looking for such things as striations and fresh color. If you have one you can use a simple multi-meter in resistivity mode on one of your pieces or on a grain and see if it is conductive which will mean it is metallic Fe-Ni alloy. 

 

I'd guess magnetite grains in those pieces. It could be pyrrhotite, an iron sulfide mineral that can be magnetic and you might smell sulfur if you heat some ground up material with a torch. The bottom pic with the shinny face is intriguing. There is a naturally occurring Fe-Ni alloy mineral called awaruite that occurs in peridotites and serpentinites but I don't know anything about the geology of Texas or if ophiolite complexes occur there which have those rock types but the Precambrian Texas Craton does outcrop in central Texas so who knows. A quick Google search shows some interesting geology there. 

 

Awaruite also occurs in meteorites. 

 

For future trips where one is looking down instead of up at the sky, for not too much money a person can purchase a small 16x hand lens, a set of hardness picks and a pencil magnet. As well a small steel or plastic gold pan is handy (especially if you're finding heavy minerals like magnetite in a stream bed). And a good rock and mineral field book is always money well spent. We amateur astronomers should always be ready to put on our amateur geology hat - just in case. 

 

Neat find and good pictures to. Happy prospecting and keep us posted.



#5 quietlifeboy

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Posted 14 March 2016 - 11:10 AM

Thank you North of Sixty for the detailed response! Very helpful information. I will acquire the stuff you suggest for my next hunt and try to use a bit of porcelain as a streak plate. I still think I have something terrestrial but one can dream!



#6 lee14

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Posted 14 March 2016 - 04:46 PM

If those are strongly magnetic, it's very unlikely they are meteorites. The window you exposed looks granular, if you were to expose a similar surface on an iron meteorite, it would not display a pattern at all. To see the widmanstatten pattern, which is a certain indicator that a subject is indeed a meteorite, it would have to be etched with acid.

 

You can post your pics here for additional feedback:  www.facebook.com/groups/meteorite.or.meteorwrong/ 

 

Keep looking!

 

Lee




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