Tuesday, November 9, 2010

River cobbles

This past weekend we went up to Llano for a class field trip. Along with the plentiful granites up there, we checked out a serpentinite quarry, where I picked up a few pieces with nice chromites - tiny, glittering specks embedded in magnetite layers. Spinel is a really cool mineral. I've really warmed up to spinel lately, having a newfound admiration of it. They are little engines that definitely could - recording melt depletion despite massive whole-rock metasomatic events. Spinel has hidden beauty you can only see under reflected light, it can take on a multitude of forms and textures in peridotites, from euhedral to holly-leaf shaped, sometimes wormy, or variably intertwined with garnet. Here's a spinel that underwent some sort of breakdown. You would never guess that such an unassuming mineral could have such a spectacular texture.

OK and back to the Llano trip - here is a very interesting river cobble I picked up.

You never know what you might find in a river.

On a final note, I like Daylight Savings Time more this year than last. I feel somewhat more in tune with the seasons than a few weeks ago, when I was feeling completely discombobulated.

1 comment:

Cin-Ty Lee said...

nice spinels. the hornblendite is what fascinates me the most. i was searching for those on the way back up the creek so i could get myself a piece. nice find.