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

FIRST PLACE: Shirley Whitmore for
“My dog puked that up in the back yard after eating some
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.


Trifarina said...

I think this game is too hard without the actual rock, or maybe I'm just a sore loser. There's no way I would have missed ooids in person.

The dog vomit guess was rather graphic....

Fault Rocks said...

Based on the overall results from week #1, I'd say that my students have the advantage of the handlens but they can't make it work for them! This is another kind of nasty one - so I will maybe go easier in week 3? Gotta keep the students on board. WWHD?

Lost Geologist said...

if the foto would be bigger it would be easier to recognise the details. i couldnt see any ooids in the last one.

anyways. this one is also sedimentary i think.

i think i can recognise some clasts and rounded pebbles. perhaps this is a conglomerate with carbonate matrix? could also be sand or so. its too small to recognise.

dobarah said...

My school has moved me to the mathematics department of our school (that is a stretch as there are only 2.083 of the teachers in the math dept) so I shared your great blog with our 1 science teacher. Perhaps I'll get her to learn to knit too?

Fingel said...

I think its some kind of Tuff. Maybe Biotite or Olivine? Hard to tell.

Lost Geologist said...

so what's the solution?