minerals s6e5.b investigate the composition of rocks in terms of minerals

MINERALSMINERALSS6E5.b Investigate the composition of rocks in terms of minerals.

WHAT IS A MINERAL?WHAT IS A MINERAL?

•A mineral is a naturally formed, inorganic solid that has a definite crystalline structure.

MINERAL STRUCTUREMINERAL STRUCTURE

•To understand “crystalline structure”, you need to know a little about the elements that make up a mineral.

MINERAL STRUCTUREMINERAL STRUCTURE

•Elements: pure substances that cannot be broken down into simpler substances by ordinary chemical means.

•All minerals contain 1 or more of the 92 naturally occurring elements.

MINERAL STRUCTUREMINERAL STRUCTURE

• Each element is made of only 1 kind of atom.

• Atom: smallest part of an element w/all of the properties of that element.

• Minerals are made up of atoms of one or more elements.

MINERAL STRUCTUREMINERAL STRUCTURE•Most minerals are made of compounds of several different elements.

•Compound: a substance made of two or more elements that have been chemically joined or bonded. Ex: NaCl (halite)

MINERAL STRUCTUREMINERAL STRUCTURE

•Native elements: a mineral that is composed of only one element.

•Ex: gold & silver

MINERAL STRUCTUREMINERAL STRUCTURE

•Crystals: solid, geometric forms of minerals produced by a repeating pattern of atoms or molecules that is present throughout the mineral.

MINERAL STRUCTUREMINERAL STRUCTURE

• Each mineral has a definite crystalline structure.

SILICATES vs. NONSILICATESSILICATES vs. NONSILICATES

•Minerals divided into 2 groups based on chemical composition

•Minerals that contain a combination of silicon & oxygen are silicate minerals.

•Silicate minerals make up more than 90% of the Earth’s crust.

SILICATES vs. NONSILICATESSILICATES vs. NONSILICATES

•Minerals that do not contain a combination of silicon & oxygen are nonsilicate minerals.

•Classes: native elements, carbonates, halides, oxides, sulfates, & sulfides.

IDENTIFYING MINERALSIDENTIFYING MINERALS

•Color•Luster•Streak•Cleavage & Fracture•Hardness•Density•Special Properties

COLORCOLOR• Not the best way to identify a mineral• Same mineral can come in a variety

of colors• Ex: Quartz---purest state is clear;

impurities can cause it to be different colors

• Exposure to air & water can change color (Ex: pyrite---usually golden but changes to brown or black when exposed to air & water)

LUSTERLUSTER• Luster: the way a surface reflects

light• Shiny or dull = luster• Metallic, submetallic or nonmetallic

luster• Shiny = metallic luster• Dull= submetallic or nonmetallic

luster

STREAKSTREAK• Streak: color of a mineral in

powdered form• Rub mineral against a piece of

unglazed porcelain (streak plate)• Mark left on streak plate is the streak.• Color of streak not always the color of

the mineral sample.• Not affected by air or water• More reliable than color in identifying

a mineral

CLEAVAGE & CLEAVAGE & FRACTUREFRACTURE

• How a mineral breaks• Determined by arrangement of

atoms• Cleavage: tendency to break

along smooth, flat surfaces (Ex: halite & mica)

• Fracture: tendency to break unevenly along curved or irregular surfaces (Ex: quartz)

HARDNESSHARDNESS• Mineral’s resistance to being

scratched• Mohs Hardness Scale• Ranges from 1 to 10; 1 being

softest & 10 being the hardest• A mineral of a given hardness

will scratch any mineral that is softer than it is.

DENSITYDENSITY• The measure of how much matter

is in a given amount of space.• Density is a ratio of an object’s

mass to its volume• D=m/v• Measured in grams per cubic

centimeter (g/cm3)

DENSITYDENSITY•Water has a density of 1g/cm3

•Used as a reference point for other substances.

•Object sinks---it’s density is greater than 1g/cm3

•Object floats---it’s density is less than 1g/cm3

DENSITYDENSITY• Ratio of an object’s density to

the density of water is called the object’s specific gravity.

• Ex: specific gravity of gold is 19. That means gold has a density of 19 g/cm3.

• 1 cm3 of gold contains 19 times as much matter than 1 cm3 of water contains.

SPECIAL PROPERTIESSPECIAL PROPERTIES

•Some properties are particular to only a few types of minerals

•Fluorescence, chemical reaction, optical properties, magnetism, taste, radioactivity