Finally learned the name for the type of rocks I've found in Sweetwater County, Wyoming: Dreikanter.
Dreikanters are a type of ventifact that usually forms in desert or peri-glacial environments due to abrasive action of blowing sand.
They characteristally have a 3-faced pyramidal shape.
the word Dreikanter is German and means "a three-sider".
Here are photos I've taken of ones in my possession now:
These are filling up the seat of my computer chair.
Note however that not all of them have three sides.
But they are all made of the same type of black rock, found in a treeless desert where the wind blows all the time, and sand has given them shine (luster).
Same rocks on chair, different angle. I lightened photo because the black color of these rocks makes it hard to make out their angular features.
Here I've lightened the photo to display the angles, etc. of these rocks. They are very dark in color in reality.
I converted this photo to greyscale color (true black & white) and sharpened the photo.
This is often found in same area where I found the dreikanter rocks, and is made of the same type of rock. The difference is that they have a bumpy texture on their exterior. They are the exact same black color as the dreikanter rocks above.
Here is one with an American Penny Coin on top to show the size of the stone.
Another image converted to greyscale (true black & white color).
These rocks are very heavy and make great paperweights or door stops!
Here is a large true dreikanter (3-sided) boulder embedded in the ground in the desert.
It bears some rust colored patina near bottom probably from the red sand.
This one has 4 sides.
This is my favourite one. It looks like a large leaf.
This one is about the size of a teenager's footprint.
A Fish- Shaped rock.
This thin, flat specimen is nearly perfectly symmetrical. It fills the entire palm of my hand.
This one only has 2 sides.
This one is diamond shaped and has a bumpy surface.
Here they are laid out on a carpet. No two are alike!
Last ones...until I go back this summer and find more!
Petrified Wood beginning to agatize. Found south of Wind River Canyon, Wyoming.
Now why didn't I bring this rock home? It has such an amazing pattern.
Oh yeah, thats right -- I'm trying to leave the huge specimens at home since I live in a small apartment! (Besides, I already have several hundred pounds of rocks!)