FMF - Friends of Minerals Forum, discussion and message board

[Gerhard Brandstetter]

A historic specimen:
This comes from the first reported find of Euclase from Austria (Köchlin 1886). The original finder tried to protect his "valuable" discovery. He mentioned several wrong locations for this. Here given as from "Graden im Mölltal". Finds few years ago suggested that the correct locality should be "Krumkkeeskopf Mtn.".

[Gerhard Brandstetter]

Again something from Austria. Mainly from very small finds.

[Gerhard Brandstetter]

A little update with Namibian minerals - enjoy!

[Carles Millan]

[Gerhard Brandstetter]

Art from mother nature

[Jamison Brizendine]

I agree with Carles. My favorite specimen you uploaded was that Austrian scolecite!

[Roger Warin]

Very nice specimens and photos. I appreciate the input.
Can I comment on kamacite?
Roger.

[Gerhard Brandstetter]

Thank you all for your nice commments. Please feel free to comment on my Gibeon Meteorite, Roger Warin. Interesting discussions are always welcome!

[Roger Warin]

Hi Gerhard.
Pictured meteorite is an octahedrite. This octahedral crystalline structure is essentially an alloy of consisting of two phases of nickel-iron, kamacite and taenite. Putting together these two phases is based on epitaxy.
Taenite has a higher percentage of nickel. It solidified from a solid solution of iron and nickel at a higher temperature. Kamacite solidified at a lower temperature. The nickel content of the metal solid solution is decreased by crystallization of taenite and thus kamacite can crystallize.
This whole process of crystallization is extremely slow (and it can be done only in space) at a rate of 50 to 300°C/Myr. Nickel in metal solid solution is partially depleted by crystallization of Taenite. Thus kamacite can crystallize, with Ni diffusion. Then the cycle starts again: because the alloy is enriched in Ni, a new crystallization of taenite can occur. Other intermediate phases also exist, such as plessite (a supersaturated solid solution of a mix of taenite and kamacite in the fields between the bands).

Widmanstätten Patterns are obtained by surface corrosion of the slice with nitric acid or other acid such ferric chloride mixed with water or another acid to form a solution. The wider bands are kamacite (it’s a result of the bulk composition of the metallic meteorite, called an iron).
Kamacite is more easily dissolved than taenite by acid and thus the plate structure is revealed upon etching. The angles between the bands are dependent on how the meteorite is cut.
This octahedral structure is seen as a pattern when a polished slice is etched chemically.
There are coarse, medium or fine octahedrites.
Roger.

[Gerhard Brandstetter]

Hallo Roger, thank you very much for the interesting aspects and additional informations about my Gibeon Meteorite. It is highly welcome!

Usually i do not write too much in this Forum because my english is limited and the knowledge of most members is very high. I love it!!!! Other thing is that this is not a meteorite forum of course. But fact is that meteorites consists of different Minerals and will have a good place here from time to time. I have over 100 samples....... - with a very open eye to the mineralogical components. So i loved to read your fine description of Octahedrites.

Nice greetings from Austria, Gerhard

[Roger Warin]

Hallo Gerhard,
I know that this forum does not talk about meteorites. That's why I asked you for permission to add a comment. But terrestrial rocks are not excluded from discussions in this forum. However igneous extraterrestrial rocks are very similar to terrestrial rocks, and even a little simpler. The study of irons gives a partial idea of what is the core of the Earth.
Extraterrestrial rocks have given a new impulse in petrology studies, I think.
At the limit could we post on this forum a photo of a single euhedral mineral (of course a minute crystal) having crystallized in space?
Best regards,
Roger.

[Gerhard Brandstetter]

In the past few days i tried to take some photos of self collected micros from a now closed quarry in the Austrian Alps. Small clefts yielded alpinoptype minerals. I do not have stacking control - so all stacks were done by hand. The only lense i used is a reversed standardzoom 18-55 mm. Now i hope you have some fun with it!

[Roger Warin]

Hi Gerhard,
Sure, I had fun with your last post: very nice specimens and stunning photos. There are a lot of oxides in this quarry. I don't know Aeschynite-(Y).
What program do you use to complete the stacking?
Roger.

[Gerhard Brandstetter]

Thank you, Roger!
Aeschynite-(Y) is not the only rare mineral here. I have two big boxes full of micros waiting for photos..... The quarries of Lohning and nearby Kaiserer are famous for rarities! A large article about it was in Mineralogical Record Vol. 44, No. 6 November - December 2013. During the active time I had a lot of collecting trips to Rauris - love this valley!

For stacking I use the old CombineZP and for fine tuning the ancient Photoshop7.

[Pierre Joubert]

Hi Gerhard. Fantastic photos! The last few photos, are they really(red) schorl?