Minerals Chapter 4

Atomic Theory Atoms are made up of Protons, neutrons, and electrons. Protons and neutrons are in the nucleus. Electrons are in a cloud around the nucleus.

Atomic Theory Atomic Number – tells you the number of protons in the nucleus Always a whole number The atomic mass tells you the number of protons AND neutrons in the atom. Usually a decimal The word ATOM means NEUTRAL SO in an atom…the number of protons is the same as the number of electrons

Example If I have an atom that has 11 protons, the atom is sodium. If there are 12 neutrons, the atomic mass is 23. Since it is an atom, the number of electrons is 11. **Electrons are not part of the atomic mass because they don’t weigh enough.**

You try it! How many protons, neutrons, and electrons does an K atom have? Answer, p= 19, n= 20, e = 19 If you have an ION, there are a different number of electrons. If you have a positive ion, one or more electrons was lost If you have a negative ion, one or more electrons was gained.

Oxygen is most abundant element Some abundant metals Silicon is second most abundant; aluminum is third 04.10.b1 Iron is most abundant transition metal

Inter- molecular force Sharing Loaning Free flow Stick together Inter- molecular force Metallic bond Covalent bond Ionic bond

Atoms can bond by loaning electrons Atomic Bonding Space for one more electron in outer shell One electron in outer shell Atoms can bond by loaning electrons

Properties of Water Molecule Oxygen and hydrogen share electron Water molecules are polar Polarity helps water dissolve other compounds + side - side 04.13.b

What is the difference between a rock and a mineral? Minerals – Most minerals in geology consist of 2 or more elements chemically combined. Some minerals are composed of one element. Ex. Diamond Rocks - a naturally formed combination of minerals.

What is a mineral? Solid – definite crystalline structure Ex. Ice is a mineral, liquid water is not Natural – Cannot be synthetic, found in nature.

What is a Mineral continued Inorganic – Formed without any influence from plants or animals ie, never living Ordered Internal Structure – Molecules occur in an organized, repeating pattern

What is a mineral continued… Specific Chemical Composition – Contains atoms of chemicals in standard ratios. Ex. Halite (table salt) – Sodium and chlorine in equal amounts. NaCl Ex. Calcium carbonate – CaCO3

How Do We Distinguish One Mineral from Another? 5 Characteristics Used to Classify Minerals Crystal Form Cleavage/Fracture Color Luster Microscopic Observations

Tests for Identifying Minerals Hardness- resistance to being scratched by another object. Streak- trail of broken material left on a porcelain plate Effervescence- reaction to diluted HCl

Identifying Tests Continued Magentism- magnetic properties Specific Gravity – Density in relation to water. ***

MOHS Hardness Scale The hardness of 10 minerals are ranked relative to one another. (p.81)

Crystal Shape When growing, the outward shape of a crystal mimics the minerals internal structure. Forms a crystalline lattice.

Crystal Shapes There are 6 crystal systems Cubic system- 3 axes of equal length that intersect at 90°angles Orthorhombic system- 3 axes of different lengths, intersect at 90°angles

Crystal Shapes Tetragonal System- 3 axes intersect at 90° angles. 2 axes are equal in length. Triclinic System – 3 axes intersect at oblique angles.

Crystal Shapes Hexagonal System – 3 axes of equal length intersect at 60° angles. The 4th axis (vertical) can be a different length. Monoclinic System – 3 axes, each of different length, intersect, with 2 intersections at 90° angles and the third at an oblique angle.

Effect of the Environment on Crystals In order for a crystal to grow into its natural shape it must be unimpeded by surrounding material. Minerals that grow within rocks or near other crystals are not fully formed.

Causes of Cleavage Cleavage is controlled by the arrangement of atoms in a mineral and the strength of the bonds between atoms. In order to break apart a mineral you must cleave bonds between the atoms. The mineral breaks at the point with the weakest bonds.

Brown atoms bonded with blue atoms into flat sheets (strong bonds) Sheets joined by long bonds between sheets (break along weakest bonds)

Fracture When bonds all have the same strength the mineral will not break in specific areas but will break in any direction. Mineral breaks through the lattice in nearly any direction so it will fracture

Types of Cleavage Cleavage can occur in multiple directions One direction 2 perpendicular directions 2 non-perpendicular directions 3 perpendicular directions 3 non-perpendicular directions

Observe the number of cleavage planes in this mineral MEDIA 0405c1_biotite.mov INSTRUCTIONS TO STUDENTS Observe the number of cleavage planes in this mineral EXPLANATION One main direction of cleavage cutting through a mineral that grew in six-sided crystals

Observe the number and relative orientation of cleavage planes in this mineral MEDIA 0405c3_pyroxene.mov INSTRUCTIONS TO STUDENTS Observe the number and relative orientation of cleavage planes in this mineral EXPLANATION Two perpendicular directions of cleavage (at right angles)

Observe the number and relative orientation of cleavage planes in this mineral MEDIA 0405c5_amphibole.mov INSTRUCTIONS TO STUDENTS Observe the number and relative orientation of cleavage planes in this mineral EXPLANATION Two non-perpendicular directions of cleavage (planes can intersection at angles other than 90 degrees) 04.05.c

Observe the number and relative orientation of cleavage planes in this mineral MEDIA 0405c7_halite.mov INSTRUCTIONS TO STUDENTS Observe the number and relative orientation of cleavage planes in this mineral EXPLANATION Three perpendicular directions of cleavage; breaks into cubes 04.05.c

Observe the number and relative orientation of cleavage planes in this mineral MEDIA 0405c9_calcite.mov INSTRUCTIONS TO STUDENTS Observe the number and relative orientation of cleavage planes in this mineral EXPLANATION Three non-perpendicular directions of cleavage; breaks into shapes like squashed boxes 04.05.c

Periodic Table Letters are abbreviation for element # is atomic number (number of protons)

Mineral Classification There are 7 classes of minerals Silicates- contain oxygen and silicon Carbonates- contain carbon and oxygen Oxides- oxygen bonded with a metal

Mineral Classification Cont Halides- contain chlorine and flourine Sulfates- contain sulfur combined with oxygen Sulfides- contain sulfur combined with a metal Native minerals- contain a single element.

Major Classes of Rock-Forming Minerals Oxides Halides Carbonates Silicates Sulfides Sulfates Native minerals