Rock of the Week #2

1. Minerals
2. Rock Name
3. Tectonic environment

... this one doesn't fizz!

edited to add, by request from the lost geologist:

Scale bar is ~ 1cm.

Here's the solution to the last Rock of the Week #1:
Rock of the week #1:
the answer!

This rock is an ooid dune sediment from San Salvador
Island, The Bahamas. The grains are “ooids”: layered,
spherical carbonate grains which precipitate in the surf
zone on a high-energy beach. The grains were blown by
the wind into an aeolian dune. The wind sorted the ooids
into ripples with coarse grains on the crests and fine
grains in the troughs. Ripples migrating along the dune
face left laminated layers of coarse/fine ooids. The
current pyramidal shape of the hand sample is a
coincidence of erosion.

1. (1 pt) What is the dominant mineral?

: Calcite (carbonate also accepted)

Hons students who wrote “quartz” will write “I will not
forget the Mohs Hardness Scale” 100 times using a
stick of a mineral of hardness 7.

2. (2 pt) How did this rock form?
: “shallow marine precipitation” got a point
: “ooid” or “oolite” got a point

AWARDS OF THE WEEK:
FIRST PLACE: Shirley Whitmore for
“My dog puked that up in the back yard after eating some
bones”
RUNNERS UP: Ian & Tim for
“ Plaster of paris. Christie made it. You can’t fool a bunch
of fools”

Well, little grasshoppers, at least you got the cation right.