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What is it #2
  
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Andrew Harvey




Joined: 20 Sep 2016
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PostPosted: Nov 22, 2017 13:37    Post subject: What is it #2  

Hi again - another specimen that has me stumped (easy to do nowadays!) I picked it up on one of my walks in Cornwall, probably Cligga Head but not definitely. Jet black, measuring 33 x 32 x 25mm and feeling light, weighing just 19gms. It is slightly friable. The top has many small crystals of no regular shape that I can determine; the bottom has roughly square plates in rows and columns. All crystals are highly lustrous. Picture one shows the top, picture 2 shows the plates. I am sorry that the quality of 2 is not better; I was sweet-talked into buying a cheap digital microscope ....


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 Dimensions: 33 x 32 x 25mm
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Pic 2LR.jpg
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Pete Modreski
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PostPosted: Nov 22, 2017 16:28    Post subject: Re: What is it #2  

I am thinking you have a piece of coal. Does it feel THAT light?
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Andrew Harvey




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PostPosted: Nov 23, 2017 13:31    Post subject: Re: What is it #2  

Hi - I am sure you are right about coal. I haven't seen a lump of coal for over 40 years but this has a likeness to the coke that my granny used to burn, although that did not have the crystals on it. It is very light; a piece of sphalerite of similar size weighs 60 gms, 3 times as much. I suppose I could see if it burns on the basis that if it does it is coal and if it doesn't then no harm will come to it! Thanks for your interest. I will try and get an accurate measuring jug to calculate displacement etc. Kind regards
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Pete Modreski
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PostPosted: Nov 24, 2017 12:47    Post subject: Re: What is it #2  

Andrew, I think that what looks like crystal faces on your piece of coal, is just the way the coal breaks. It tends to fracture along flat, perpendicular planes; it's a type of cleavage, and in coal mining, this kind of fracturing is traditionally known as "cleat".
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Andrew Harvey




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PostPosted: Nov 24, 2017 20:57    Post subject: Re: What is it #2  

Thank you Pete - I have consigned them to the log basket. Kind regards
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Peter Perkins




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PostPosted: Nov 25, 2017 04:34    Post subject: Re: What is it #2  

Andrew, I have followed this thread, with a smile! Can I suggest that you offer these strange specimens to your local school. We don't want the next generation to grow up knowing about coal but not knowing what it looks like. From Peter in Norfolk (UK).
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Andrew Harvey




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PostPosted: Nov 25, 2017 13:28    Post subject: Re: What is it #2  

What a good idea Peter. oh and by the way I am delighted if my slight embarassment has caused merriment in East Anglia!

During the last two years I have taken a very broad brush approach to collecting and as I learn more I realise that this is not the right way for me to go. So I have spent a wintry day getting some of my specimens ready for sale. I like to buy but not sell at auction. I could set up my own web page but would be ranked on the millionth page and no-one would ever find it so the dreaded eBay looks like the only option.

I am not sure what next. As I live where I do, Cornish minerals would be the obvious choice Sulphides interest me, so do silicates so maybe a collection of one of those with a tray or two of Cornish beauties....

Kind regards
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