Minerals

Building Blocks of MatterAn element is a substance that cannot be

broken down into simpler substances by chemical or physical means

The basic unit of matter is the atom (smallest particle of matter that retains characteristics of an element)◦Atoms are made of subatomic particles:

protons (+), electrons (-), and neutrons◦Protons (atomic number) and neutrons

reside in the nucleus◦Electrons move around in energy levels

outside of the nucleus

Building Blocks of Matter

Building Blocks of MatterAtoms of the same element but with

different neutrons are isotopes◦Carbon-12, Carbon-13, Radioactive

Carbon-14

Building Blocks of MatterTwo or more elements can combine to

form compounds (H2O)Properties of compound differ from the

elements◦Ionic bonds form between positive and

negative ions (element loses or gains electron)

◦Covalent bonds involve sharing of electrons between elements (H2O)

◦Metallic bonds form when electrons are shared by metal ions

Building Blocks of Matter

MineralsMineral is a naturally occurring,

inorganic solid, with an orderly crystalline structure and a definite chemical composition◦Natural, not man-made (synthetic)◦Solid at normal Earth temperatures◦Crystalline- atoms or ions are

arranged in orderly repetitive manner

◦Consistent element (gold) or chemical compound (quartz [SiO2])

◦Inorganic

How Minerals FormCrystallization from magma as it coolsPrecipitation occurs when water

evaporates leaving the dissolved substances can react to form minerals

Changes in pressure and temperature can cause atoms to rearrange

Hydrothermal solution (water and dissolved substances between 100C-300C) form new mineral when come in contact with mineral

Mineral GroupsMinerals are classified based on their

compositionSilicates are composed primarily of

silicon and oxygen◦Make up 95% of all minerals on Earth◦Ferromagnesian minerals contain a lot

of the elements iron and magnesium (usually dark in color)

◦Nonferromagnesium silicates are usually light in color because they don’t contain iron and magnesium

Mineral GroupsSulfides have compounds combined

with sulfur◦Galena (PbS), sphalerite (ZnS)

Carbonates have compounds made up of a carbon atom and bordered by oxygen

Halides contain elements that combine with halogen ion (chlorine, fluorine, bromine, iodine)◦Salt is a halide mineral called halite

Mineral GroupsSulfates contain compounds made of

sulfur enclosed by four oxygen atoms (CaSO4)

Oxides contain element combined with oxygen◦Hematite (rust)

Native elements are elements in relatively pure form ◦Gold (Au), Copper (Cu)

Properties of MineralsMineral’s properties can help identify

themHardness is a mineral’s resistance to

scratching◦Moh’s hardness scale ranges from 1-

10◦10 is diamond, talc is 1

CleavageCleavage is the breakage along planes

of weakness (based on atomic arrangements)◦One direction: mica breaks into

sheets because bond holding sheets together is weak

◦Two directions: feldspar breaks into two directions at about 90 degrees

◦Three directions: calcite, 75 degrees

Fracture and StreakFracture occurs when minerals don’t

show cleavage when broken◦Break along curved surfaces, splinter,

or just break unevenlyStreak is the color of the mineral in its

powdered form◦Created by rubbing mineral across

streak plate◦More reliable than color of mineral

(small amounts of different elements can change color of mineral)

ColorSapphires have different colors based

on small amounts of different elements

Luster and Crystal FormLuster describes how light is reflected

from the surface of a mineral◦Metallic luster- have metallic

appearance◦Glassy- quartz; earthy- chalk

Crystal form is the visible expression of a mineral’s internal arrangement of atoms◦If allowed to form slowly and without

space restrictions they form consistent crystal shape

Density and Acid TestDensity is the ratio of an object’s mass

to its volume (D=m/V)◦Density of a pure mineral is a

constant valueAdding dilute HCl to an unknown

mineral is the acid test◦If the sample fizzes, it is a carbonate◦The fizz is carbon dioxide