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1340 Views 13 Replies Last post: Jan 9, 2014 9:34 PM by Tabfish RSS
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Jul 5, 2013 3:39 AM

Shiny rock/stone of some kind, silver?

Hello internet

 

So I've come across this rock/stone of some kind, it really shines when moving it around in the light, noticed it also has some copper like colour vein runing through it.

 

It weighs 480g, length 11cm. wide 8cm, thickness 2cm
Where it is from, unknown but I got it from my garage I'm from NewZealand so it might be from a tourist spot around the country, just my guess.

 

http://iforce.co.nz/i/qrihjirl.xyz.jpg

http://iforce.co.nz/i/jnqch4op.2et.jpg

 

Any tips would be great

 

Thank you

  • Currently Being Moderated
    Jul 5, 2013 7:28 AM (in response to Goosestav)
    Re: Shiny rock/stone of some kind, silver?

    It is a lump of mica shist, a metamorphic rock, probably formed deep underground in the core of a mountain range as it was being built. Mica schists are very common in orogenic terranes worldwide.

     

    There look to be two types of mica in your specimen: a light one (probably muscovite) and a dark one (probably biotite). It is those micas that provide the reflections. Micas are phyllosilicate minerals - silicates with a parallel-layered structure like wads of leaves (phyllo is Greek for leaf). Each layer can reflect the light, so with a transparent phyllosilicate like muscovite, a wad of them can be very glittery.

     

    There will be other minerals as well, in grains too small to ID from a hand specimen (thin section and microscope needed). Some of those could give rise to iron oxides during weathering, which may explain the brassy patches (which may or may not be your 'copper like colour vein runing through it'.

     

    Mike

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      • Currently Being Moderated
        Jul 5, 2013 9:10 AM (in response to Goosestav)
        Re: Shiny rock/stone of some kind, silver?

        You're welcome.

         

        If you're an information junkie...

        [apologies to the general NaturePlus readership for this being off-topic]

         

        You might also be interested to know that the plastic laminate 'Formica' got its name from its early use 'for mica' in electrical components, before the days of the transistor. It is a very good insulator; it was used internally in thermionic valves and elsewhere. (The name has nothing to do with formic acid, as some folks think).

         

        Formica became well known in the 1950s+ for decorative purposes (tabletops, railway carriage linings, etc.). In that form it was produced with patterns printed on paper and interlaminated near the top of the structural layers all impregnated with phenolic or melamine resin as usual and surfaced with Melamine. The big sheets (9x5ft in the USA) then went under heat and pressure to make the finished product.

         

        But before then, it was made differently, using a woven fabric and Bakelite resin. That product had similar electrical properties to mica, but was much easier and cheaper to produce in large quantities than mica.

         

        I know about this because my father, William J. Hardman introduced Formica to the UK. While working for Thomas de la Rue, he was also involved in the development of a prototype carriage for Great Western Railways, which used plastic laminates. He was also a consultant to the BBC, coaching Barry Bucknell on how to DIY with Formica (Barry used to present 'Barry Bucknell's Do It Yourself' in the 1950s). Barry was somewhat renowned for mishaps during his shows, which actually made for more-interesting watching! My Dad, too, would have the odd mishap, usually involving the unceremonious wrapping of the damaged finger with masking tape. I grew up helping Dad with his own DIY, and have a collection of artefacts to do with Formica, including exhibition items. It is in my blood!

         

        Now here's the funny thing...

        The Formica brand has had various owners, but it it currently held by Fletcher Building, a company based in your very own New Zealand!

         

        See also;

        - http://en.wikipedia.org/wiki/Formica_(plastic)

        - http://www.formica.co.nz

         

        Mike

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