Chapter 7 Section 1
I Mineral Resources
- more than 3000 minerals in the earth’s crust
- two types of minerals
- metals
- gold, silver and aluminum
- shiny (luster)
- able to be bent (malleable and ductile)
- good conductors of heat and electricity
- nonmetals
- sulfur and quartz
- dull surface
- poor conductors of heat and electricity
A. Ores
- native elements – metallic minerals that exist in
earth’s crust as nuggets of pure metal (Au, Ag, Cu)
- compounds – two or more elements chemically bonded
1. Ores Formed by Cooling Magma
a. Cr, Ni and Pb
b. as the magma cools, dense metallic minerals sink
and accumulate at the bottom of the magma
chamber
2. Ores Formed by Contact Metamorphism
a. Pb, Cu and Zn
b. contact metamorphism
1b. process that occurs when magma comes
into contact with existing rock
2b. changes the composition of the rock
c. hydrothermal solutions
1c. hot fluid solutions
2c. moves through small cracks in a large mass
of rock
3c. minerals from the surrounding rock dissolve
4c. new minerals precipitate from the solution
and form narrow zones of rock called veins
5c. lode – a mineral deposit within a rock
formation
3. Ores Formed by Moving Water
a. movement of water helps form ore deposits
b. placer deposits
1b. a deposit that contains a valuable mineral
that has been concentrated by mechanical
action
2b. metals are released from rock during
weathering
3b. stream currents carry the minerals until
the stream current cannot carry them any
further
B. Uses of Mineral Resources
1. some metals are prized for their beauty and rarity
(Au, Pt and Ag)
2. gemstones
a. a mineral, rock or organic material that can be
used as jewelry or an ornament when it is cut
and polished
b. display an extraordinary brilliance
c. Table 1 page 157
C. Mineral Exploration and Mining
- in general, an area is considered for mining if it has at
least 100 to 1000 times the concentration of minerals
that are found elsewhere
1. Subsurface Mining
a. mineral deposits located below earth’s surface
b. subsurface mining – retrieval of minerals from
below earth’s surface
2. Surface Mining
a. mineral deposits located close to earth’s surface
b. surface mining – overlying rock is stripped away
to reveal the mineral deposits
3. Placer Mining
a. placer deposits are mined by dredging
b. large buckets scoop up the sediments and dense
minerals are separated from the surrounding
sediment
4. Undersea Mining
a. nodules – lumps of minerals on the deep ocean
floor that contain Fe, Mn and Ni
b. these deposits are very difficult to mine because of
their location