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2299 Views 3 Replies Last post: Dec 20, 2013 10:10 PM by MikeHardman RSS
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Dec 19, 2013 6:26 PM

Ore? rock? (meteorite?)

I work as a landscaper. We found these after rotovating the ground for turfing at a job in Croydon.

The smaller one is 20 x 25 x 30mm and weighs 83g. 18cm3  density 4.61

The larger one is 55 x 50 x 35mm and weighs 232g.  42.5cm3 density 5.45

I just used a litre measuring jug to work this out but can use a smaller jug another time.

The colour is silver with a very slight bronzy tinge though I have only wiped them off with a wet rag. Not sure if I could clean them more in some way?

They are heavy and metallic but not magnetic.

The small one is just kind of squarish but the bigger one has a few cavities of 10-20mm and one side with <5mm dips on which is darker or more tarnished.

It leaves a dark grey mark when scratchd on a white tile.

Please, somebody, what are these things.



Message was edited by: jody1 Worked out more accurate volume.15cm3 and 45cm3


Message was edited by: jody1 Density 5.533333 and 5. 13333

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    Dec 18, 2013 12:55 PM (in response to jody1)
    Re: Ore? rock? (meteorite?)



    There are a few possibilities, mainly: meteorite, industrial slag, natural mineral/rock.

    The information you've provided so far helps, but we need some more.


    1. We need a fairly accurate value for each of their volumes, so we can make reliable calculations of their denisty. That should help a lot in narrowing the list of candidates. I appreciate you have given us some dimensions, but they would not really give a good enough idea of volume. Better to use a displacement method: for instance: find a container just bigger than the specimen (do one at a time), fill it to the brim with water, carefully put it inside a larger container without spillage, carefully put the specimen into the smaller container so the larger one catches the displaced water (maybe use a fine wire to hold the specimen when lowering it), remove the specimen then the smaller container, measure the volume of water in the larger container. ...You get the idea. The more careful you can be with the water, the better.

    This method assumes the specimens do not soak up much water and that they don't contain cavities, andthat they are fairly homogenous (all of which seem reasonable in this case).


    2. Have a look at these resources; you should be able to make some headway yourself while I am dealing with the volume numbers you will give me.

    - how to identify a meteorite -

      (also a useful table of densities)





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        Dec 20, 2013 10:10 PM (in response to jody1)
        Re: Ore? rock? (meteorite?)



        Thanks. I am slow to respond because an edit, unlike a followup posting, does not generate an email.

        So: silvery, non-magnetic, and density 5.1-5.5g/ml, dark grey streak, slightly prone to bronzish tarnishing (probably oxidizing).


        Let me share my thought process...


        The density is right for haematite, but the colour and streak are wrong.

        The density and streak is right for magnetite, but the magnetism is wrong.

        Zinc looks similar, but the density and streak are wrong.

        Antimony and gallium look similar, but the densities are wrong.

        Radium and europium are about the right density, but unlikely to be found in their elemental form.


        In terms of density, colour, lustre and streak, there are quite few possibilities in terms of metallic minerals



        Some candidates (minerals and metals):

        - arsenopyrite (though density is a bit high - 6.1g/ml)


        - vanadium (tarnishes at room temperature (OK), though density is a bit high - 6.0-6.1g/ml)


        - arsenic (density slightly high: 5.7 g/ml)


        - molybdenite (but it is very soft; I suspect too soft; can you scratch your specimen with a finger nail?)


        - gallium (similar, a bit harder)

        - germanium (density 5.3 g/ml is OK)



        And there are others, especially alloys.


        We could narrow the range of possibilities further by considering hardness. But that would probably still not get us an exact ID. More detailed tests would be needed, mostly in a lab. If you have concerns about health issues, by all means take the specimens to your local environmental health office - who may run some tests in their labs. If you do so, and you get an answer, please let us know!


        For now, bearing in mind what we know at the moment including where you found them, I suspect they could be industrial waste, for instance from metal working and/or perhaps related to aircraft during the Second World War (thinking of Croydon Aerodrome). The surface texture suggests 'man-made' and 'industrial' to me.


        I hope that has been of some help; I am sorry not to be able to give you an ID.



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