This document contains descriptions and background information about several rock samples collected from locations in California. It includes details about obsidian collected in Bishop, granite from Raymond, staurolite "cross rocks" from Chowchilla, a sedimentary rock with embedded rocks from Chowchilla, and a metamorphic rock near a slough in Chowchilla. For each rock, it provides information on physical characteristics, how it was identified, and geological context of where it was found.

1. Field Assignment
Part 1
Lenai Munch
Geology
Judy Horn
Due May 15, 2011

2. Obsidian

3. Description
Obsidian is an extrusive igneous rock also
known as volcanic glass.
This rock is similar in look to a glass. It is a
black color with the glossy look to it. The
particular piece that I found had once been used
by a Native American most likely, because it
has been changed in original shape to make the
appearance of an arrowhead. The texture is
smooth but can be sharp around the edges.

4. Background Information
Bishop California
Bishop is where I was born and raised and growing up there we always
looked for pieces of obsidian that had been made into arrowheads. The
main areas we find them are in the desert area when we are horseback.
The desert in which they are found usually consist of the sand,
sagebrush and other rcoks. There are obsidian domes in the area that
were formed by volcanic eruptions 550 to 600 years ago. The sticky
lava reached the surface and cooled quickly without allowing crystals
to form which then forms the glass like obsidian. As time has passed,
obsidian pieces have spread and can be found around Bishop. In the
past Native Americans used obsidian to form arrowheads which is most
interesting to come across. From our backyard we have found many
pieces. There are multiple volcanoes around Bishop including
Mammoth Mountain and some others close by which could have at
some point been the reason for the obsidian around the area.

5. Granite

6. Description
Granite is an intrusive felsic
igneous rock.

7. The granite rock is gray in color with
specks of black. Granite is formed by
intruding into another rock. This
igneous rock is formed by magma. The
rocks are intruded into the Earth’s crust.

8. Background Information
This piece of granite that I found was in
Raymond California. Nearby
Raymond is Yosemite National Park
which contains the half dome. The half
dome is a granite rock formation. There
is also a huge granite area in Raymond
that you can see from driving by on the
road.

9. “Cross
Rocks”
Chowchilla
California

10. Description
These rocks are actually a silicate mineral called
staurolite crystals. They are more commonly
known as “cross rocks”
This was harder to identify and research. The rock
I found is prismatic in shape with four sides.
When the rock is rinsed off it is a red color in
appearance with a blackish colored cross in the
middle hence the name cross rock. The
picture shows the cross up close.

11. Background
I found these rocks in Chowchilla
California in the horse arena. They are
small but abundant in this area.
Through research I found that they are
not commonly found in very many
places in the world.

12. Cross Rocks
These rocks through time have become
symbols of myths, tales and
superstitions. Many religions believe
these rocks have good faith and luck.

13. Sedimentary Rock

14. This rock that I found is gray with
smaller rocks embedded within it as well
as a pink or red color throughout the
rock. I identified this rock as a
sedimentary rock because multiple other
rocks inside. The texture seemed to be
clastic. I found this rock in Chowchilla
California.

15. Metamorphic Rocks

16. Description
This rock was a lighter tone of black with white
streaks running through it and some hints of
a reddish color throughout the rock. I was not
positive on my identification of this rock but
the reason it made me believe that it was
metamorphic was because of the streaks of color
like layers in the rock. It seemed as though the
colors got there through some chemical change. I
found this rock near a slough in Chowchilla
California where water is often running.