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Properties of Minerals
Mineral
5 characteristics:
– naturally occurring (not
made by people)
– inorganic (cannot come
from living things)
– solid (definite shape and
volume)
– crystal structure (regular, repeating pattern)
Element
Compound
Crystal Shape
pure substance that cannot be broken down
makes up all minerals
made of one kind of atom (smallest part of an element)
two or more elements chemically combined
determined by arrangement of atoms
Silicate Minerals
Nonsilicate Minerals
contains a combo of silicon, oxygen, and one or more metals
make up more than 90% of crust
ex. quartz, feldspar, mica
does not contain compounds of silicon and oxygen
ex. copper, calcite, fluorite
Identifying Minerals
Color
Streak
-easily observed physical property
-only a few minerals ALWAYS have the same color
-color of a mineral’s powder
-streak color does not vary, even though physical color can
-observe by rubbing on porcelain tile
Luster
Density
-how light reflects off surface
-ex. shiny, metallic, glassy, earthy, waxy, pearly
-mass in a given space (M/V)
-density always stays same, no matter what size the mineral is
Hardness
Mohs Hardness Scale
-test invented by Friedrich Mohs
-ranks 10 minerals from softest (1) to hardest (10)
-scratch test
-softest = talc
-hardest = diamond
Cleavage
Fracture
splits easily along flat surfaces
-depends on how crystals are arranged
-ex. mica
-breaks apart in an irregular way
-shell shaped, jagged, crumble
-ex. quartz
Special Properties
-fluorescence: glows under UV light
-magnetism
-optical: bends light
-reactivity: reacts to acids
How Minerals Form
Crystallization
Geode
-atoms are arranged to form materials with a crystal structure
-forms two ways:
1. magma/lava
2. materials dissolved in water
-round, hollow rock
-lined with mineral crystals
Minerals from Magma/Lava
-form as hot magma cools inside crust; lava hardens on surface
-liquid to solid state
-size of crystals depends on rate at which magma cools
*deep below surface – cools slowly = large crystals
*close to surface – cools quickly = small crystals
Solution
Minerals from Solution
-mixture
-one substance completely dissolves in another
-elements and compounds dissolved in water leave a solution
-crystallization occurs
Formed from Evaporation
Formed from hot water solutions
-when solutions evaporate, water turns to gas and leaves minerals behind to crystallize
-ex. seas evaporate leaving behind gypsum and calcite
-magma heats ground water
-minerals dissolve in water
-as solution cools, minerals leave solution and crystallize
-ex. Gold, copper, sulfur, pyrite.
Vein -narrow channel of mineral different from surrounding rock
-solutions of hot water and metals flow thru cracks in rock
-metals crystallize into veins
-resembles streaks of fudge in ice cream
Mineral Resources
Gemstones
-hard, colorful mineral with glassy luster
-valued for color, luster, and durability
-mainly for jewelry and decoration
Metals -source of metals like aluminum, iron, copper, and silver
-useful for:
*stretching into wires,
*flattening,
*hammering without breaking
Other Uses
Ore
-used in foods, medicines, fertilizers
-ex. talc = talcum powder
quartz = glass & watches
gypsum = cement, stucco
-rock that contains metal or useful mineral
-metals & minerals can be separated from ore
Prospector
Mining
-anyone who searches for ore deposit
-look for certain features on earth and study maps of rocks
-three types:
strip mines
open pit mines
shaft mines