Geology 1303-Block 2Minerals

Rock CycleIgneous Rocks-(including volcanoes&plutons)

Sedimentary RocksMetamorphic rocks

Exam 2 :Oct 18th WED -To be Confirmed

• What is a mineral?

• How do we differentiate a mineral from a piece of wood or a human?

• What is a rock?

Minerals

• What is a mineral? Naturally occurring (not man-made) Inorganic Solid (not made of liquid or gas) with a definite

chemical structure which give it unique physical properties.

Minerals vs. Rocks

• There are nearly 4000 known minerals - but most rocks are formed by only a few dozen minerals.

• Rocks are aggregates (mixtures) of minerals. So . . . minerals are the building blocks of rocks.

• A question for the future: How do minerals come together to form a rock?

Composition and Structure of Minerals

• To understand how minerals form, we need to understand the characteristics of elements and atoms.

• Chemical Elements Elements are the basic building blocks of

minerals. There are over 100 known elements.

Composition and Structure of Minerals

• Atoms smallest particle of matter that exhibits all the

characteristics of an element. Atoms are made up of:

Nucleus, which contains Protons (atomic number)- positive electrical charges and Neutrons - neutral electrical charges (P +N = atomic mass)

Shells which surround the nucleus and contain Electrons - negative electrical charges

• The weight (density) of an element depends on the number of protons and neutrons in the nucleus.

Combining Elements to Form Minerals

Elements combine with each other to form a wide variety of minerals (chemical compounds)

Atoms combine chemically by gaining, losing, or sharing and electron with other atoms. (opposites attract) (pg-26)

The new mineral (compound) will have very different physical properties from the elements that combined to form it.

Combining Elements to Form Minerals

Since rocks are mixtures (not chemical combinations) of minerals, minerals keep their physical properties within a rock.

Is it possible for two different minerals to have the same chemical composition?

YES! Both diamond and graphite are made of carbon. The difference between these two minerals is the way in which the carbon atoms are arranged.

Mineral Properties

• Minerals have lots of different properties that help us identify them. Crystal form, Luster, Color, Streak, Hardness, Cleavage, Fracture, Specific gravity, Taste, Smell, etc.

Rock Forming Minerals

• The most common rock forming minerals are composed of 8 elements: Oxygen (O) , Silicon (Si), Aluminum (Al) , Calcium (Ca) , Sodium (Na) ,

Potassium (K) Iron (Fe) and Magnesium (Mg)

• There are just a few dozen minerals that we call the rock-forming minerals.

Composition of the Crust

• The most abundant elements in Earth's crust are: Oxygen (46.6% by weight) Silicon (27.7% by weight)

The crust

Silicate Minerals

• Silicate minerals, minerals built primarily from silicon-oxygen tetrahedrons, are the most common rock-forming minerals.

• Silicate minerals are grouped according to how the tetrahedrons are arranged in the mineral.

Silicate Mineral Groups

• Olivine - independent tetrahedrons (Mg, Fe) • Pyroxene group - tetrahedrons are arranged in

chains (Mg, Fe) • Amphibole group - tetrahedrons are arranged in

double chains (Mg, Fe, Ca) • Micas - Tetrahedrons are arranged in sheets

Two common types of mica: Biotite (dark) (K, Mg, Fe, Al), Muscovite (light) (K, Al)

Silicate Mineral Groups

• Feldspars - Three-dimensional network of tetrahedron Two common types of feldspars:

Orthoclase (K, Al) Plagioclase (Ca, Na) Most plentiful mineral group

• Quartz - three-dimensional network of tetrahedrons (SiO2)

Mineral Color

• Mineral color is often governed by presence of Mg, Fe (dark) or absence of these elements (light).

Non-Silicate Minerals

• Major groups: Oxides (FeO2), Sulfides (PbS), Sulfates (CaSO4), Halides, "Native" elements (gold), Carbonates (limestone, marble) (CaCO3)

Mineral Resources

• Ore - rock that contains useful metallic minerals that can he mined at a profit.

• Since 98% of the Earth's crust is made up of 8 elements, an element/mineral has to be concentrated at levels above normal for profitable mining.

Rocks

A Rock

is an

Aggregate

of

Minerals

Quartz Amphibole Feldspar

Structureof an Atom

Nucleus

Electron

Nucleus (neutrons &protons)

Chemical Compound

Na+ Cl-

NaCl

Silicon-Oxygen

Tetrahedron(SiO4)

Isolated Tetrahedrons(Olivine)

Tetrahedron Arrangement

Single-Chain Double-Chain Sheet

Pyroxene Amphibole Mica

Mohs hardness scaleMohs hardness scale

10. Diamond 4. Fluorite

9. Corundum 3. Calcite

8. Topaz 2. Gypsum

7. Quartz 1. Talc

6. Potassium Feldspar

5. Apatite

• Please do not use WebCT for email

• aellis@utep.edu

• Minerals Cont.

• Rocks and the Rock Cycle

For Next Time

• How do minerals "mix" together to form rocks?

• What is the rock cycle ?