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Xenolith??? Peridotite

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Merry Christmas All,

I found this 10.2 gram rock on Willcox Playa in south eastern Arizona. Leaves a very faint grey or brown streak and it is attracted to a magnate. Been trying to figure out what exactly it is for about a year. At first I thought it was a xenolith, but then I read that a xenolith is covered with basaltic magma. The exterior of this rock looks to be the same green material on the interior just burnt or altered some how (one of the pics is the magnified exterior). I took it to an armature geologist friend and he was pretty sure it is epidote because there are some small clear or white quartz crystals in with the green crystals. When I looked for images of epidote nothing looked even similar to this rock. So now I am thinking it may be peridotite. You guys have any ideas?




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Yeah. It looks like Olivine basalt. There are craters just south of town that are just filled with the stuff. Many of the tiny "bombs" look just like that.

I think it is probably peridot. I forgot exactly how that goes but I think the light green phase is peridot and the dark green Olivine. If I remember correctly it is all Olivine from space and peridot/Olivine in terrestrial rock.

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7 hours ago, Desertpilot said:

I agree with bedrock. Paramore crater and the rest of the San Bernardino valley volcanics have Olivine deposits. Makes you wonder how it got to Wilcox lake bed?

Maybe it put on mast and just started sailing.:rolleyes::rolleyes::rolleyes:


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The Potrillo Maar is not too far East of Wilcox. The entire crater is Olivine basalt. 

I don't know how far those things flew when the craters popped but you can find Olivine many miles to the west.

Wilcox playa is just a hop, skip and a big jump from here. I know the basalt can be found on the playas just east of the Peloncillo Mtns. Wilcox is not too far to the west from there.

That stuff is pretty common in volcanic that come up from great depths. No telling exactly how it got to Wilcox playa but there are plenty of possibilities. Lots of that debris went way up into the air in violent explosions. They say debris from the Jemez eruption covered the ground several feet thick for hundreds of miles. You would assume that little pebbles from the Potrillo Maar could have been launched high enough to wind up in Wilcox.

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