The Rock Cycle

ROCKS are naturally occurring solid mass of minerals, remember they have to be inorganic - so things like coal cannot be rocks because they are made from organic materials. The three major types of rocks are igneous, sedimentary and metamorphic.

Important- the energy that drives the Rock Cycle comes from the Earth's interior (igneous and metamorphic rocks) and from the Sun (weathering for sedimentary rocks).

• When magma cools igneous rocks can form intrusive (below ground) or extrusive (above ground).
• Compaction and cementation (lithification) from the weathering of surface rocks for sedimentary rocks.
• Metamorphic rocks occur deep in the ground from the processes of high temperatures and high pressures.
  

Recap on Minerals

A few more facts on minerals:

• composition and structure determines the properties of a mineral.
• density of a mineral is determined by dividing the mass by the volume
• density is a very important property of a mineral, ex: to tell if a sample of gold is gold check the density of the sample.

Mineral Identification

Physical properties of minerals include:

• crystal form- shape, arrangement of atoms
• cleavage- tendency to break with a smooth plane
• fracture-uneven breakage of a mineral
• luster- how light is reflected from the surface
• color- obvious, but not very reliable
• streak- color of a mineral in powder form
• density- ratio of mass/volume
• hardness- resistance to abrasion, using Moh's scale of hardness
  

Mineral Formation

Minerals are formed in the Earth's crust by four major processes:

• magma- molten rock in the crust, as it cools this magma crystallizes to form minerals.
• precipitation- as water evaporates, the dissolved minerals are left behind (ex. limestone, gypsum).
• high pressure/high temperature- these minerals can recrystallize deep within the Earth's crust.
• hydrothermal solutions- hot water and dissolved substances can come into contact with existing minerals, and react to form new minerals.
  

Mineral Composition

Minerals are classified by their composition, the elements that they are made of. As seen by the graph ( left) the most abundant element in the Earth's crust (by weight) is oxygen.

The major mineral groups are:

• silicates- (above right) this is the most common mineral group as it contains oxygen and silicon. ex. feldspar
  
• carbonates-contain carbon and oxygen, ex. limestone
• oxides- contain oxygen and a metal element, ex. TiO2, rutile
• sulfates/sufides- contain sulfur, hint-all minerals in this group contain sulfur. ex. pyrite
• halides- contain a halogen (salt formers) ex. halite-table salt.
• native - minerals of only one element, ex. gold
  

Minerals

Minerals typically are composed of two or more elements and have the following properties:

• inorganic- not derived from living things
• naturally occuring- not "fake"
• solids- cannot be a liquid or gas
• crystalline shape- orderly arrangement of atoms
• chemical composition- definite composition

An interesting note that "ice" from a glacier is considered a mineral.

Thanks to Philip Staublin for pointing out that there are some minerals that are considered "native minerals" composed of only one element. This is for Philip- good catch- we did cover native minerals in class but it is not going to be a test question- so I did not blog it, Mr. V.

Week of 2/6/12

A reminder to all classes. Unless instructed otherwise email me all work as a PDF attachment.

Chemistry
Monday- Lincoln Tech, watch "Kahn" lecture Balancing
Tuesday - balancing equations Ch 11
Wednesday- Ch 11, computer lab
Thursday- Ch 11
Friday- computer lab writing assignment


Physical Science
Monday- Wise choices, watch Rock lecture
Tuesday- rock samples, rock cycle
Wednesday- computer lab, 
Thursday- rock reinforcement
Friday- rock ID