Naked Science Forum

Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Gummo on 20/08/2021 15:45:04

Title: Mineral ID
Post by: Gummo on 20/08/2021 15:45:04

Good afternoon.

My grandson has just found this mineral on the shores of the River Foyle at Derry in the North of Ireland.

Any chance you could ID it please?

Title: Re: MIneral ID
Post by: Bored chemist on 20/08/2021 16:32:22

When the geologists see this they will ask questions like
Is it hard or soft?
Is it noticeably "heavy" i.e. is it dense?


It might be amber, or it might be polyurethane.
Or lots of other possibilities.
Is there anything else you can tell us about it?

Title: Re: MIneral ID
Post by: Gummo on 20/08/2021 16:37:07

Thanks for that.

Just got this from The Natural History Museum:

It’s an attractive piece. I can understand why your grandson found it interesting – it has a gem-like quality. Unfortunately it is glass. One can see the conchoidal (shell shaped) fracture. This is a diagnostic feature of glass.

Title: Re: MIneral ID
Post by: Bored chemist on 20/08/2021 18:00:27

I saw the conchoidal fracture.
It indicates that there's little or no crystal structure- sorry it rules out ruby :-)
Glass is a very probable answer.
But it doesn't rule out amber (or plastic).
Is it soft enough that you can scratch it easily with an iron nail?
Can you chip a bit off and see if it melts in a match or candle flame?

One interesting possibility, though an unlikely one...
http://www.chrisboyne.com/Cordite-Cove
which is why I don't suggest setting the whole thing on fire.

Title: Re: MIneral ID
Post by: Gummo on 20/08/2021 18:02:00

I'll get back to you when I get my hands on it.

Title: Re: Mineral ID
Post by: Gummo on 21/08/2021 17:39:58

I have it now - it's extremely hard.  With great difficulty, I was able to chip off a tiny fragment (pin-head size).  I then applied flame from a lighter for approximately 15 seconds - it didn't make any change in the fragment.

Although, red in the hand, when held up to an overhead light, it's distinctly amber.

Title: Re: MIneral ID
Post by: Bored chemist on 21/08/2021 17:50:57

It seems very likely that you have a piece of red glass.

It might still be pretty if you tumble polished it. :-)

Title: Re: MIneral ID
Post by: Gummo on 22/08/2021 14:35:38

Tumble polishing - what's the easiest/cheapest means of doing that?

Title: Re: Mineral ID
Post by: Bored chemist on 22/08/2021 16:01:13

Check eBay and the like for people who have realised that having a machine that tumbles rocks 24/7 is noisy and annoying and are selling a rock tumbler.

Title: Re: Mineral ID
Post by: Gummo on 22/08/2021 20:05:59

Ha-ha!  Thanks very much for indulging me.