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Identity HelpHelp to identify.

7th Oct 2019 04:30 UTCPaul Famularo

Hi all,
I was digging a trench in my back yard for storm water.
I came across sandstone, clay and what looks to be coal like.
Then I dug this out which was very different to what I've found before and rinsed it off. The first thing that I noticed was that it felt heavy for its size and obviously its shape which is round but also egg shaped.
Any help would be much appreciated.
I'm from Australia and don't live far from a lake 
Thank you.

7th Oct 2019 04:31 UTCPaul Famularo

Another photo on its side

7th Oct 2019 13:18 UTCEd Clopton Expert

The worn surface and weathering make it difficult to say what this is.  It could be coarse sandstone, granite, or even volcanic porphyry.  A freshly broken surface might give more information.  An indication of size would be helpful, too, either state its measurements or include a familiar object in the photo: your hand, a coin (with diameter stated for non-Australians), car key, etc.

8th Oct 2019 06:50 UTCPaul Famularo


Ed Clopton Expert  ✉️

Hi Ed,
Thank you for your reply.
At its longest point it's almost 3 inches long and 2.5 inches wide.
Thank you

7th Oct 2019 17:29 UTCDonald B Peck Expert

Paul,  Trying to identify (put a name to) a mineral, and especially a rock, is very difficult to impossible given only a photo.  That said, I am curious about the blue (?) crystals in your rock.  Are they really blue, or is the color a bit off?  Are they transparent of opaque? 

And welcome to mindat.

8th Oct 2019 06:59 UTCPaul Famularo

Hi Donald,
Thank you for the reply and welcoming me.
I would say a they are light grey and the little speckles glisten

8th Oct 2019 11:22 UTCKeith Compton Manager

More info needed on locality - Aus is a very large area and narrowing it down will help with the geology.

Also, if it's from your backyard in a built up area it may well have been filled with rock and other material from elsewhere.

8th Oct 2019 11:56 UTCGabe Farnsworth

Possibly some kind of Arkosic Sandstone, or could be a concretion around a nucleus, which is why cracking it open or slicing may help. Other possibilities, rhyolite porphyry, or even andesite. Will watch with interest to see if one of the experts can suss it out for you!
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