Are these iron meteorites?

[sjastro]

I found these using a metal detector.

They are magnetic and do not leave a residue when scraped against an unglazed bathroom tile (a test to differentiate from earthly hematite and magnetite which do leave a residue.)

Thanks for any assistance.

Steven

[Blue Skies]

No, they don't look right to me. No fusion crust.

Have a look at this site - Meteorwrongs (http://meteorites.wustl.edu/meteorwrongs/meteorwrongs.htm). There are lots of non-meteors on them and they explain why. See if anything matches your 'find' there.

[sjastro]

Thanks for your comments.

There are definite signs of fusion crust on the back of the right hand object in the first image. Unfortunately it requires a macro image which is beyond the scope of my camera or I would have to cross section a sample.

Incidentally these samples are quite heavy for their sizes.

I'm thinking of testing the samples using X-ray spectroscopy.
I believe a high nickel content is a property for iron meteorites.

Regards

Steven

[gregbradley]

Maybe you've made a mineral strike and your new nickel mine can fund a 30 inch RC!

Greg.

[jjjnettie]

You can send them to Sydney and have them tested. But it's rarely worth the cost of sending it down, unless it's of significant size.
In which case one should photograph the suspect in it's original location and use a sat nav to get accurate coordinates.

I highly recommend the book "Field Guide to Meteors and Meteorites" by O. Richard Norton and Lawrence A. Chitwood.

[sjastro]

Ah yes but if the nickel is from an iron meteorite then exporting a 30" RC is illegal.:D

Regards

Steven

[renormalised]

How big are they Steven??

If they're big enough, cut one in half length ways. If you see a cross hatched pattern of crystal growth (Widmanstatten Lines) after etching and polishing, then it's definitely a meteorite. But some don't have the pattern....it's due to nickel content in the rock.

It's actually very hard to tell what they are from those piccies. Where did you find them?? If they're terrestrial, they're most likely (from their colour and the weight you described) a nickel-iron ore, or an ore of some other mineral of that colour such as chromite, chromite-nickel, chromite-vanadite and/or one of the rare earths.

[sjastro]

Thanks Jeanette.

It's interesting that the samples were found in two remote locations, each location has been marked using GPS. So it's possible there is more stuff to be discovered.
Fortunately I have connections in Victoria so getting a sample tested for free shouldn't present any problems.

Regards

Steven

[sjastro]

Hi Carl,

There quite small. The object in the second image is approximately 30mm X 30mm X 10mm thick and weighs 58g.
They were found in a dry creek bed at a depth of about 75mm - 100mm below a sandy sediment. Found at two locations about 30 metres apart.

Thanks for the advice.

Steven

[renormalised]

It would be great if they turn out to be meteorite fragments, but you want to hope that they're ore samples from some of the minerals I mentioned...especially any one of the rare earths. If they are, go back to where you found them and do a stream sediment sampling survey and try and trace where they come from. Then form a mining company with someone and take a claim out on the area. Rare earths are a literal gold mine and if it's a large enough deposit you'll make squillions!!!!.

[sjastro]

Appealing to my sense of greed.

Just had a look at a map of the area, the gully is a boundary between a Historical Park and a National Park!

So much for the potential of mining.....

Regards

Steven

[renormalised]

Never stopped them before :)

If it's worth heaps of money, all the national park or historical monument legislation in the world won't matter jack. If they think they can turn a tidy profit from it and it's in the national interest, they'll mine it.

A rare earth mine, I can assure you, would be in the national interest. But it would all depend on how big the blithering idiots in Canberra were.

[DavidU]

I've often wondered what acid is used to etch the Widmanstatten lines.

[AstralTraveller]

Steve,

Would it be worth starting by checking their density (or sg as a geologist would say). You have the weight and getting the volume is easy. Even if you don't have a measuring cylinder handy you can't determine the volume of water displaced by weight difference. Just catch the overflow in a pre-weighed dish. The density of the water will be <1 but not by much.

[sjastro]

Possibly nital etching which is nitric acid + alcohol (methanol or ethanol) although I don't think this is advisable if Nickel is involved. Alternatively it could be Picric acid and alcohol.

Nice stuff Picric acid, it's explosive when dry.
A metallurgist I knew blew himself up using Picric acid.

Regards

Steven

[sjastro]

Measured SG is 7.2.
Iron meteorites are in the range 7.0-8.0.

Regards

Steven

[GrahamL]

So the geology of the area dosn't explain what you found eh ?

I think you should throw some gps coordinates into this thread to
get some more input Steven :D

[cfranks]

I used Nitric acid to etch mine (years ago) and, providing you use standard safety procedures, it is very safe. I was led to believe that Widmanstaten Lines can only be found in Meteorites due to a cooling of the original molten material at a rate of 1 degree per million years. Not my area of expertise so I can't swear to it. :)

Charles

[AstralTraveller]

A geologist just told me they are etched with fairly conc nitric. He wasn't sure off hand whether it is neat (ie straight from the winchester) or slightly diluted.

The one we have in a display here was also washed multiple times in clean water, dried in a vacuum oven for some hours and then coated with clear lacquer to protect it from rusting. The Widmanstatten pattern is very obvious.

[DavidU]

I have a meteorite I was hoping to etch to see the pattern.

[sjastro]

Found a third sample from a different location in the creek bed.
This one shows a more obvious fusion crust (if it is that) and quite a bit of corrosion.

I found a number of old gold mines "upstream" and adjacent to the creek bed which possibly suggests this may have been the original site. The objects and excavated material may have been dumped into the creek during mining.

All going well three samples from the three different locations will be tested using X-ray spectroscopy by a former employer. The spectrometer will analyse for all elements in the range from Sodium to Uranium. If there is a large Nickel content it should confirm the objects are iron meteorites.

Regards

Steven

[sjastro]

The power of X-ray spectroscopy.

No nickel found in the samples = a meteorwrong.

Regards

Steven

[renormalised]

Ironstone...most likely hematite. That "melt crust" would be a weathering patina. It's probably part of the ore out of which they were mining the gold. Either that, or capping materials to the ore body...a gossan. Quite common surface indicators of subsurface ore bodies.

[sjastro]

Ironically I gave a sample of hematite crusted basaltic rock ("melt crust") as a reference sample for testing.
The key is the presence of silicon in the sample (as silicate).

One of the meteorwrong samples was cross-sectioned and revealed iron under the corrosion.
Without doubt this a man made object.

Below is the spectrum of the basalt rock. Don't get excited about the Rhodium peaks, they are from the X-ray tube.:)

Regards

Steven

[renormalised]

Just noticed a manganese peak tucked in on the iron peak....this is mangalloy. It could be just flakes off some of the old equipment left at the mine after it closed. Most probably off a ball mill or stamping mill.