But what is that phenocryst? The diamond shaped "arrows" in the upper left say amphibole, but there are 90-90 cystal edges and octagonal truncations elsewhere. No internal cleave that I can see.
Could be both amphibole and pyroxene. Don't you yearn for a thin-section?
Really, it reminds me of euhedral to subhedral olivine phenocrysts. More specifically, it reminds me of peridote crystals out of the Kilborne Holes diatreem of New Mexico, famous for its large olivine crystals.
These however, appear to be psuedomorphs composed of iddingsite (or any of a hundred other alteration clays) after (Mg?) olivine. I seem to remember a basalt from Hawaii characterized by phenocrystic olivine. Was it called Hawaiite? I made a thin section suite of Hawaiian basalts once, kinda reminds of that. Maybe more so, the peridotite from the Kilborne Holes was quite macroscopic (jem quality, sometimes) while the Hawaiite displayed smaller, randomly oriented pheno's.
Is that what is weathering out in the un-RAT'd surface?
Good list o' minerals. If you include twinned metamorphic minerals, don't forget staurolite, a personal favorite! And I'm still hoping to see evidence of sulfides, don't tempt me, please.
Oh, If you are playing with this image, try some edge-enhancement - it brings out those phenocrysts.
Happy (almost, here) New Year.
Space/Science » in reply to re: Smooth inclusions in Wishstone rock.
porphyritic basalt
The whole thread (59 posts)
- Smooth inclusions in Wishstone rock.
- Squires on Wishstone
- UPDATE: Wishstone Rich in Phosphorus
- re: Smooth inclusions in Wishstone rock.
- Non-crystalline material?
- porphyritic basalt