Properties of Minerals

November 11, 20157th grade Chapter 9.1

Meme Moment

Symbols for Molecules

HBrO4

Each atom has a symbolfrom the periodic table Symbols can be 1 or 2 letters.

First = capital, second = lower case or none

Numbers say how manyNo number = 1

Mineral Molecules

CaSO4· 2H2O

This dot shows up in a lot of minerals’ chemical formulas.

It means that for every CaSO4 molecule, there are

2 H2O molecules in the same place. Together, they make gypsum

MineralsMineral: naturally occurring solid that can be formed by inorganic processes, has a crystal structure, and a defined chemical composition

• Defined chemical composition means that it’s a single type of molecule, so you can also call a mineral a substance

• 5 traits to define a mineral

Dioptase (CuSiO3·H2O)

5 Traits of Minerals1. Naturally occurring

o You can make things that look like minerals in a lab, but they’re not “official” minerals unless they’re also found in nature.

2. Solid3. Crystal Structure

o Flat sides, sharp edges (based around prism shapes from math class!)

4. Forms by inorganic processeso You can sometimes form minerals in the body (e.g. kidney

stone), but it’s not an “official” mineral unless you can also make it with things that aren’t plants or animals

5. Definite chemical compositiono You can write a chemical formula for them

Identifying MineralsMinerals are identified mainly by their physical properties

1. Color2. Streak3. Luster4. Hardness5. Density6. Crystal structure7. Cleavage8. Fracture

Marcasite (FeS2)

StreakStreak: color of a mineral’s powder.

• Sometimes different shapes of the same mineral look like different colors, but when you grind them up, it will be the same color

• This used to be very important for making paint!

Lazurite ((Na,Ca)8[(S,Cl,SO4,OH)2 · (Al6Si6O24)])

LusterLuster: how shiny a mineral is/how light is reflected from it

• Uses words like metallic, glassy, earthy, silky, waxy, greasy, pearly

Fluorite (CaF2)

HardnessHardness: how easy it is to scratch a mineral or scratch something else with it

• Measured with Mohs hardness scale• 1= soft, 10=hard

Azurite (Cu3(CO3)2(OH)2)

Cleavage & FractureCleavage: splits easily along flat surfaces

Fracture: what it looks like when it splits

Pyrope (Mg3Al2Si3O12)