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3759 Views 6 Replies Last post: Apr 1, 2014 4:24 PM by Freddy Fieldmouse RSS
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Mar 27, 2014 11:59 AM

Strange greeny blue magnetic rocks - meteorite?

I have added three more images this time taken by USB microscope - sorry I couldnt work out how to show the magnification factor. I hope these help the identification. They really have me scratching my head.


Also hardness is at least 7 (scratches glass) and density about 2.5 (I thought it was more until I tested it in kitchen).




Found at a building site excavation in Suffolk, UK. Theser rock/mineral fragments are dense, slightly magnetic,shades of green/blue and "greasy" to the touch. They seem to have sheered cleanly and have an almost "glassy" appearence. Some have internal "debris" in the shape of marbles. Hopefully the pictures will allow identification.


There is a small magnet I attached to one of them to illustrate magnetic/metallic properties.Any views welcome.odd rocks.jpg140326_0011.jpg

  • Blast furnace slag?



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      • Yes - glass slag.


        Note that glass does not necessarily refer to silicon dioxide glass; various materials in an amorphous state can be called glass. In this case, the green colour could be related to ferrous iron.


        Since we are mentioning magnetic glass, here's once instanace -


        And here is something more esoteric - spin glass.

        I just have to copy the text here, even though it is not actually that relevant, just because it is a nice example of jargonistic obfuscation"

        "A spin glass is a disordered magnet with frustrated interactions, augmented by stochastic positions of the spins, where conflicting interactions, namely both ferromagnetic and also antiferromagnetic bonds, are randomly distributed with comparable frequency. The term "glass" comes from an analogy between the magnetic disorder in a spin glass and the positional disorder of a conventional, chemical glass, e.g., a window glass."

        ...from a very technical Wiki entry -



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          • Darkish greenish-blue - copper compounds.

            Pale blue-grey - not sure of actual elemental cause, but it is a common colour in flints and related cryptocrystalline forms of silica.

            Marbles: probably globules of molten something-else, remaining distinct from the glass due to higher melting point.

            Not related to lightning strike - fulgurites are very different.


            Bear in mind that a lot of slag from industrial processes such as smelting is used for roadstone and other constructional purposes. In that way, it can end up a long way from the indstry that created it.



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