What is a mineral? How do we differentiate a mineral from a piece of wood or a human? What is a rock? - PowerPoint PPT Presentation

Geology 1303-Block 2MineralsRock CycleIgneous Rocks-(including volcanoes&plutons)Sedimentary RocksMetamorphic rocksExam 2 :Oct 18th WED -To be Confirmed

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

• 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.

• 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?

• 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.

• 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.

• 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.

• 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.

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

• 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.

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

The crust

• 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.

• 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)

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

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

• 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

Quartz

Amphibole

Feldspar

Electron

Nucleus

Nucleus (neutrons &

protons)

Na+

Cl-

NaCl

Isolated Tetrahedrons

(Olivine)

Single-Chain

Double-Chain

Sheet

Pyroxene

Amphibole

Mica

Mohs hardness scale

10. Diamond 4. Fluorite

9. Corundum 3. Calcite

8. Topaz 2. Gypsum

7. Quartz 1. Talc

6. Potassium Feldspar

5. Apatite

• aellis@utep.edu
• Minerals Cont.
• Rocks and the Rock Cycle

• How do minerals "mix" together to form rocks?
• What is the rock cycle ?