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Volcanic specimen

Posted by Junior Sto  
Junior Sto January 11, 2019 11:28AM

I wanted to get some opinions if I can put this specimen in the volcanic bomb category or some other type of volcanic material.
It is from a river valley in Buzau county in Romania.
It was collected 8 years ago and I washed away some lime deposits with anti-calc liquid. This treatment had some unwanted results because it rusted some flakes embeded in the crust and whitened what apears to be some kind of transparent glazing.
It’s magnetic so I assume it is a magnetite.
I wil post a little later the XRF results and a macro of a part of the ?ablation? crust.
open | download - 25114F94-740E-4363-9598-C8361167D6E0.jpeg (2.93 MB)
open | download - 6EDB7C4C-8ADB-4D3E-B9F8-F445443157A5.jpeg (3.01 MB)
open | download - F741D39C-0345-467C-BF63-08CECBC51F1E.jpeg (3.24 MB)
José Zendrera January 11, 2019 12:36PM
Looks like a volcanic bomb of basalt rock, which, among other minerals, always contains magnetite, hence the observed magnetism.
Gregg Little January 17, 2019 07:30PM
Another possibility is a chunk of pillow lava. IF it is basalt then this is more likely a flow feature rather than ejecta which is more commonly found with intermediate to acidic composition lava.
Paul Brandes January 17, 2019 07:48PM
Probably not a volcanic bomb.
More than likely, this is some sort of relic of the Berca Mud Volcanoes although the colour is a bit off (maybe from the "treatment" you gave it?).
Junior Sto March 14, 2019 09:42PM
Since I managed to gather more data on the subject I will share it here.
First test I did with a small slice was an XRF test.

Junior Sto March 14, 2019 09:46PM
And today I finally got the X-ray powder diffraction test results.

Junior Sto March 14, 2019 09:55PM
And also some very nice thin slices. In a few of them you can see at the top of the picture some nice olivine skeletal crystals.
I got an input from one of my friends that the Augite is really Hedenbergite.
Note the red mineral, I have troubles identifying it (maybe chromite?).

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