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Geology 1303-Block 2 Minerals Rock Cycle Igneous Rocks-(including volcanoes&plutons) Sedimentary Rocks Metamorphic rocks Exam 2 :Oct 18 th 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.
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Geology 1303-Block 2MineralsRock CycleIgneous Rocks-(including volcanoes&plutons)Sedimentary RocksMetamorphic rocksExam 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 Rockis anAggregateof Minerals Quartz Amphibole Feldspar
Structureof an Atom Electron Nucleus Nucleus (neutrons & protons)
Chemical Compound Na+ Cl- NaCl
Silicon-OxygenTetrahedron(SiO4) Isolated Tetrahedrons (Olivine)
Tetrahedron Arrangement 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
Please do not use WebCT for email • firstname.lastname@example.org • Minerals Cont. • Rocks and the Rock Cycle
For Next Time • How do minerals "mix" together to form rocks? • What is the rock cycle ?