1) The sampling area was located in the southern Sierra Nevada mountains in California, which is primarily formed of granite dating back to the Triassic period. 2) The author analyzed 5 rock samples from the area, identifying one as granite based on its coarse grain and black/white pattern, another as schist based on its smaller grain and orange hue, and a third as marble based on its coloration from mineral impurities. 3) The other two samples were identified as limestone based on evidence of weathering, and quartzite based on its high quartz content and medium grain size formed under pressure and heat.

1. Field Assignment Part 1
Christopher Sager
Geology 1
Dec 2011

2. Sampling Area
• My sampling area was the southern Sierra-Nevada mountain range in
California. The majority of this area is formed by granite, which began to
form as long ago as the Triassic period. When the oceanic plate began to
dive under the north American plate, plumes began to form deep
underground. These plumes helped cause extensive volcanism in the area
prior to the ice age, pushing these large deposits to the surface. However
limestone, marble and schist deposits can also be found in this area.

3. Sample 1
• I believe this sample to be granite, the
igneous rock that forms the majority
of the sampling area. The grain
appears to be very coarse and has a
black and white speckled pattern
associated with high quartz and low
feldspar content. High feldspar
content in granite usually gives it a
pinkish color.

4. Sample 2
• I believe this sample to be Schist
(metamorphic) due to its smaller grain
size (compare to the granite behind it)
and its orange hue. The slight orange
tint comes from a portion of iron
oxides in the rock.

5. Sample 3
• I believe this sample to be Marble (metamorphic). Depending on mineral
impurities Marble can be almost any color.

6. Sample 4
• I believe this to be Limestone
(sedimentary). Limestone dissolves
more easily than other rocks , as
water can pick up small amounts of
carbon dioxide forming a weak acid.
This rock was probably in a stream or
river at some point smoothing its
edges.

7. Sample 5
• I believe this sample to be Quartzite
(Metamorphic) due to its appearance
of almost 100% quartz content and
medium grain. Quartzite is formed
from sandstone or chert recrystallizing
under high pressure and temperature.

8. References
• Tarbucks, E., & Lutgens, F. (2011) Earth: An Introduction to Physical
Geology. New Jersey. Pearson Education
• http://sequoia.virtualsierra.com/seqGeology.htm
• http://geology.about.com/library/bl/blrockident_tables.htm