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Author Topic: ID please  (Read 5609 times)

Salty

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ID please
« on: January 07, 2014, 12:36:18 PM »
Hi, would anybody be able to help with an ID .this crystal is black and is two pyramids base to base the bottom pyramid has a naturally formed flattened top. Just enough to stand on . Was found just north of glen. Thanks

Findem

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Re: ID please
« Reply #1 on: January 07, 2014, 12:43:34 PM »
Probably spinel (black jack). While they rarely turn up where I usually fossicked, they are common in other parts of New England.

Lefty

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Re: ID please
« Reply #2 on: January 07, 2014, 01:28:23 PM »
Hi Salty.

I tend to agree with Findem as I have found some pleonaste (black spinel) crystals at the Central Queensland gemfields that look just like that one, though smaller. The larger pieces I have found have tended to be more irregular in shape.

Jimnyjerry

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Re: ID please
« Reply #3 on: January 07, 2014, 01:59:33 PM »
Agree black spinel (pleonaste) crystal. Found them Glen Innes way as well.
I try to take one day at a time, but sometimes several days attack me at once.

Salty

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Re: ID please
« Reply #4 on: January 07, 2014, 02:56:54 PM »
Ok cool, Thanks

Aussie Sapphire

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Re: ID please
« Reply #5 on: January 07, 2014, 04:03:45 PM »
Cuts nicely as well:



Totally opaque but jet black and hard wearing in jewellery.  A much better choice compared to black onyx which is the usual stone used in black gemstone jewellery but needs to be dyed black.

cheers
Leah
Aussie Sapphire - The Lapidary Warehouse

Murf

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Re: ID please
« Reply #6 on: January 07, 2014, 04:32:30 PM »
There are a number of mineral oxides in the spinel group but I would say due to the basalt occurring in the area which you found the stone it would most likely be pleonaste which is a ferroan type of spinel. Similar to what is found in N.E Tasmania which is also derived from basalt. I have a few of the pyramid shaped ones myself which are kind of cool much better than the fragments usually found. :)
Please leave a message after the tone.....gone fossicking ;)

Aussie Sapphire

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Re: ID please
« Reply #7 on: January 07, 2014, 04:41:41 PM »
Pleonaste = Black Spinel.

See here for some more photos of this mineral at mindat.org  -  some show the crystal habit very
clearly.

http://www.mindat.org/photoscroll.php?frm_id=pscroll&cform_is_valid=1&searchbox=Pleonaste


cheers
Leah
« Last Edit: January 07, 2014, 04:48:18 PM by Aussie Sapphire »
Aussie Sapphire - The Lapidary Warehouse

Lefty

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Re: ID please
« Reply #8 on: January 07, 2014, 04:53:52 PM »
Cuts nicely as well:





Totally opaque but jet black and hard wearing in jewellery.  A much better choice compared to black onyx which is the usual stone used in black gemstone jewellery but needs to be dyed black.

cheers
Leah

Yep, my first ever go at cutting was a piece of black spinel (only ever cut about half a dozen stones). The job I did was rough as guts of course but the material itself takes on a really good polish.

Still have grandfathers old machine in the shed, maybe I'll take it up in earnest some day when I have the time.....
« Last Edit: January 07, 2014, 05:54:18 PM by Lefty »

Salty

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Re: ID please
« Reply #9 on: January 07, 2014, 05:02:28 PM »
That looks great Leah, the one in the photo above has a small chip on the bottom on a ridge line. Looking at it closely now it is 5 side emerald cut looking shape, but your description of the stone is spot on. Hopefully will get to cut it one day. Thanks for everyone's time

Salty

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Re: ID please
« Reply #10 on: January 07, 2014, 05:09:49 PM »
Sorry,to clarify I thought my stone was a pyramid either side but its pyramid top and 5 sided pyramid cut bottom. Thanks for the link.
Ron

XTMess

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Re: ID please
« Reply #11 on: January 07, 2014, 07:12:09 PM »
I'd love to cut some spinel. Unfortunately we don't come by it down in mexico. We have black tourmaline though.
Rock on...

Salty

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Re: ID please
« Reply #12 on: January 07, 2014, 07:40:30 PM »
Thanks 'Murf,
XTMess I'm hoping to get out that way in the next couple of weeks ( glen ) could post u a couple bits if it turns up not really shore on what would be deemed cut quality though. Ron

 

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