FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Hi
About olivine gem.
On Earth, there are various localities for olivine. Often black in terrestrial igneous rocks, it can be pretty when Mg content is high (forsterite).
This is often the case in asteroids.
Where is olivine (or peridot) ? In the pallasites, these meteorites, sponges of iron whose cells are filled with olivine. But these are small stones with many internal tensions. It’s difficult to cut them.
To prove its origin, one could invoke that the isotopic ratios of oxygen isotopes are depressed, but this highlighting is not within the reach of many labs.
I think it is simpler to see the planar deformations features (PDF's) in the crystal. They were caused by intense shocks as in Quartz in Shock-Metamorphosed Rocks (Impactites) in Impact Structures.
In the Esquel pallasite, I have not seen any.
Roger.