Geology of National Park Class Notes
Minerals, Rock Cycle, Igneous, Sedimentary, Metamorphic Rocks
Building Blocks of rocks.
Mineral vs. Rock:
Rocks are aggregates of minerals
Naturally occurring, inorganic solids
that possess a definite
(chemical composition). 4,000 minerals exist.
building blocks of minerals (112 known, see Periodic Table) Some minerals
made up of only one element e.g. gold, sulfur. Most elements not stable alone therefore
most minerals are a combination of 2 or more elements that form a stable
Physical Properties of Minerals
-expression of orderly arrangement of atoms. If space available.
e. g. quartz
light reflected on surface. Metallic vs. non metallic
-unreliable. e.g. quartz- impurities change color
-colored of mineral in powdered form.
More reliable than color
(Table 1.1 p. 17)
<2.5 scratched by a fingernail
2.5 to 3 scratched by a penny
3 to 5.5 scratched by a pocket knife
1.5 to 7 scratched by quartz
>7 cannot be scratched by quartz
1. TALC 2. GYPSUM 3. CALCITE 4. FLOURITE 5. APATITE
6. FELDSPAR (K)
7. QUARTZ 8. TOPAZ
****The hardest minerals make good gemstones and abrasives.
-tendency of mineral to break along planes of weak bonding. Use
micas as example.
Do not confuse with crystal form.
Minerals with out cleavage exhibit fracture. Conchoidal smooth
like glass vs. fibrous. Most minerals have irregular fracture.
wt. of mineral compared to wt. of equal vol. of H2O
9. Other: Taste, Smell, feel. Double refraction, reaction with HCl, magnetism…
***There are nearly 4000 minerals however only a few dozen are abundant and these few
make up most of the rocks of the earth’s crust. Only
elements make up the bulk of these
minerals. O, Si, Al, Fe, Ca, Na, K, Mg.
Mineral Groups: Silicates are most common rock forming.
The Rock Cycle:
Proposed by James Hutton in the late 1700’s
Three Types of Rocks and their relationships:- Igneous, Sedimentary, Metamorphic.
either beneath or at the surface to form
Exposed igneous rocks undergo
and rocks are decomposed into
is deposited by erosional agents (gravity, running water, glaciers, wind, waves). Sediment
deposited in horizontal beds and undergoes
by being compacted and cemented. This
rocks. If sedimentary rocks are buried deep within the earth the
will change sedimentary rocks into
rocks. When metamorphic rock is
subjected to greater heat and pressure it melts to create magma completing the rock cycle.