Transcript
1
Minerals
What is a mineral?
►The building block of rocks
Naturally occurring (versus synthetic) Inorganic (no C-H bonds) Crystalline solid (ordered internal
structure) Has a definite but not fixed chemical
composition
02CO, p.20
Fig. 2.3b, p.24
Chemical composition of minerals
►Elements fundmental component of matter Cannot be broken down by ordinary
means
►88 naturally occurring elements in Earth’s crust
Chemical composition of minerals
►8 elements make up 98% of Earth’s crust Oxygen Silicon Aluminum Iron Calcium Magnesium Potasium Sodium
Chemical composition of minerals
►A few elements ARE minerals (eg: gold)
►Most are comprised of 2 to 5 elements Held together by + / - electrical charges 88 elements form over 3,500 minerals 9 rock-forming mineral groups
Chemical Composition Mineral Formulas
►Quartz – SiO2 Silicon and Oxygen
►Calcite – CaCO3 (Calcium and Carbon and Oxygen)
►Olivine – (Fe,Mg)2SiO3 (Iron, Magnesium, Silicon and Oxygen)
►Potassium Feldspar – KAlSi3O8
(Potassium, Aluminum, Silicon, and Oxygen)
Table 2.1, p.24
Crystals
Crystals
►Crystal – any substance whose atoms are arranged in a periodic, repeating pattern This pattern is a crystalline structure Unit cell – the smallest group of atoms
making up the unique pattern
Fig. 2.4, p.25
Crystals
►Crystal face – flat surface occurring when a crystal grows freely Reflects light
Smaller than the mineral
Atomic size
Focus On
►Atom Nucleus
►Neutron►Proton
Electrons
►Chemical bonds Ionic Covalent
Atoms
►The nucleus of the atom contains protons and neutrons with electrons surrounding the nucleus.
Atomic Particles
►Proton – positive charge►Electrons – negative charge►Neutrons – neutral charge►Atomic number = the number of
protons in the element►Atomic mass = the number of protons
+ the number of neutrons
Chemical Formulas – Make up of a Mineral
How do I make elements stick to one another?
Bonding
►A link between atoms ( by virtue of the electrons)
►Na (by itself is a metal) plus Cl (by itself is a poisonous gas)
►But bonded together it makes NaCl – table salt
► This is Ionic Bonding – one electron is transferred to the another
NaCl Bonding
Bonding
►Carbon Dioxide – CO2
►The atomic bonding is :
Covalent Bonding
Physical Properties
How can I identify a mineral?
2.4 Physical properties of minerals
►Crystal habit the way crystals aggregate
Prismatic quartz crystals and massive quartz with no crystal shape
Physical Properties
►Cleavage Some minerals tend to break along flat
surfaces due to weak internal bonding►Fracture
The way a mineral breaks other than cleavage
Physical Properties - Cleavage
►One plane – sheets layered together►Two planes at right angles – stair
stepping►Two planes not at right angles – roof
top►Three planes at right angles►Three planes not at right angles
Physical Properties
►Hardness – Moh’s scale 1 to 10, based on minerals
►Specific gravity Density relative to water
►Color Obvious, but limited use
Table 2.2, p.31
2.4 Physical properties of minerals
►Streak Color of fine powder
►Luster The manner it reflects light
►“Other” properties – smell, taste, magnetism, striations, and reaction to HCl
Mica has a single perfect cleavage plane.
Two planes of cleavage
Three planes of cleavage
Four planes of cleavage
Fracture – no cleavage
Metallic luster of pyrite
How Do we Classify Minerals?
Based on the mineral assemblages
Mineral classes and rock-forming minerals
►Silicates
►Carbonates
►Sulfides
►Sulfates
►Native elements
►Halides
►Oxides
►Hydroxides
►Phosphates
Table 2.3a, p.32
Table 2.3b, p.32
Mineral classes
►Silicates Most abundant rock-forming minerals Over 90% of the Earth’s crust contains
silicate minerals Basic building block for all silicate
minerals – silica tetrahedra Five groups (Si:O ratio, crystal form)
Fig. 2.13b, p.33
Fig. 2.13a, p.33
Fig. 2.14, p.34
Mineral Classes
►Carbonates Forms many sedimentary rocks (CO3)
Limestone CaCO3
Photos of common rock forming minerals
Fig. 2.15a, p.35
Fig. 2.15b, p.35
Fig. 2.15c, p.35
Fig. 2.15d, p.35
Fig. 2.15e, p.35
Fig. 2.15f, p.35
Fig. 2.15i, p.35
Some Common Rocks
2.6 Commercially important minerals
►Ore minerals Metals or other elements profitably
recoverableExamples – native gold and silver, copper ,
lead, zinc►Industrial minerals
Non-metals like halite (salt, phosphates, etc) gypsum (sheetrock), sulfur, apatite
►Gems Prized for beauty & rarity, some industrial
Fig. 2.18, p.36
Fig. 2.17, p.36
Fig. 2.19, p.36
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