FMF - Friends of Minerals Forum, discussion and message board

[mineralowitz]

I wonder what it could be, but I have no idea.
The crystal is found in gneiss from Sweden.

[James Catmur]

Do you know where it came from? That might help

[mineralowitz]

It is sample from glacial erratic from Scandinavia found in northern Poland.

[Vinoterapia]

My guess go for a Zircon crystal.

[Roger Warin]

I think the same.
Zircon crystals, in the form of grains included in more recent rocks, are the oldest known terrestrial mineral witnesses. The oldest date back to 4.3 or 4.4 Ga, or 150 Ma after the formation of the planet.
The inclusion seems to be tetragonal - ditetragonal dipyramidal.
Nice find.

[mineralowitz]

Thanks for your replies. Such zircons are also found in this rock. Because they are anhedral (and that crystal in the previous micro photos is euhedral) I thought it might be something else. But on the hand, they have similar relief.

[Bob Carnein]

There appears to be a faint pleochroic halo around the crystal in your first photo. That also suggests zircon as a possibility.