4/05/2008

Rock of the Week #1

When we were out in the field, the third years told me they felt they needed more practice identifying rocks in hand sample. Of course I asked myself, "What would Hilde do? She would find a way to give a prize." Thus was born:
Each week I will put a new and different rock out in the office with 3-pts worth of questions and all the students will try to identify the rock and submit their answers. Winners for each class level are named at the end of the semester. Just for fun, I'll post the RoW here on my blog as well and you kids can play along at home. This is the e-RoW. No handlens, knife, or acid on the monitor.

RoW#1:
1. What is the dominant mineral in this rock (1 pt)
2. How was this rock formed? (2 pt)
Some third years examining RoW#1 in Shirley's office:

8 comments:

The Lost Geologist said...

Hmm...white, very porous, not very heavy (the girl easily holds it from the top with the fingers of one hand) so it could be a piece of pumice. Alternatively I also thought about chalk but alas I cannot pour acid on the screen.

p.s. It's much easier holding it in your hand and feeling it of course.

The Lost Geologist said...

forgot!
pumice: volcanic origin. gas-rich and highly viscose lava. sudden release of pressure.
chalk: microfossils of coccoliths of marin origin, usually tropical sea.

Fault Rocks said...

Ay, it is difficult to identify a rock from a photograph. But... this rock is bedded.

Trifarina said...

Geeze, no acid? That messes me up completely, and this is kind of a strange looking rock. You imply it is of sedimentary origin with the bedding comment, but that could still be some volcanically derived rock with multiple event horizons. You're tricksy. I think the handicapped web players need extra clues.

Fault Rocks said...

OK OK. it fizzes. you happy now??

The Lost Geologist said...

A bedded tufa?

Trifarina said...

I too suspect a tufa since recent posts were extraordinarily tufaceous. The high porosity is unsettling and unfamiliar, and does make me think about emplacement by fluids. Post-depositional karsting would not be so delicate. Where's Erin? Maybe this thing is from Mars.

katherine louise said...

your pics make me want to paint. have i already told you that? they also make me miss california (i know, weird- i think it's the wide open landscape)
and,
i'm SOOOO excited about rock of the week. because i know you'll pick the pretty ones ;)
thanks for keepin' up.
miss you!
k