GEO 102: Minerals

Proton

Positive (Defines the element (atomic number)) 

Change charge

Located in nucleus

Electron

Negative -

Forms chemical bonds

Determines reactivity

Located in cloud surrounding nucleus

Neutron

Neutral

Adds mass

Stabilizes nucleus

Located in nucleus

Cation

Positively charged particle

Anion

Negatively charged particle

Ionic Bonds

bonds between charged particles (ions) 

•  One element gives up electrons while the other accepts electrons 

• Occur between metals and nonmetals (typically) 

• Creates hard, brittle crystals with high melting points. Cleavage planes form where ion repulsion is greatest. Conducts electricity when dissolved in water 

Covalent bonds

bond formed by sharing electrons 

• Occur between nonmetals and nonmetals (typically) 

• Have polar and nonpolar bonds 

• Share electrons equally = nonpolar 

• Share electrons unequally = polar 

• Produces the hardest, most durable minerals. Diamond (pure C) is the hardest substance on Earth due to 4 strong covalent bonds per atom. Silicates (SiO 4 ) dominate Earth's crust via Si-O covalent bonds 

Metallic bonds

sea of electrons that float between both metals 

• Bond formed between metals 

• Explains why native metals are malleable (ions slide without breaking the bond), shiny (free electrons reflect light), and highly conductive. Native metals rarely form large deposits. 

Van Der Waals bonds

Weak electrical attractions between neutral molecules or layers caused by temporary fluctuations in electron distribution 

• Explains perfect basal cleavage — layers slide apart easily because only weak VdW forces hold them together. This is why graphite writes on paper, mica peels into thin sheets, and talc is the softest mineral (hardness 1). 

• While Van der Waals forces are not technically bonds, they are included here as many minerals exhibit these forces 

Five Requirements to be a Mineral

• Naturally Formed: Must occur in nature — not made in a lab or manufactured by humans 

• Solid: Must be in solid state at surface conditions — liquids and gases do not qualify 

• Inorganic Processes: Does not require living organisms — coal and amber are excluded (no carbon hydrogen bonds) 

• Specific Chemical Composition: Has a fixed or narrowly defined chemical formula, e.g. quartz = SiO 2 

• Characteristic Crystal Structure: Atoms arranged in repeating, ordered 3D lattice — glass does not qualify 

Crystal form

the shape of an individual mineral crystal, which is a direct reflection of how its atoms are internally arranged

Habit

describes the shape of a single crystal or a group of crystals growing together

Euhedral

crystal grows unimpeded and forms faces

Anhedral

growth is impeded, lacking well defined crystal faces

Cleavage

mineral that break in continuous uniform shapes 

a smooth, flat break that occurs along planes of weakness in the crystal's atomic structure, giving the impression of a flat crystal face

Luster

describes how light interacts with a mineral's surface, and for this course we classify it simply as either metallic or non-metallic

Color

not a reliable tool for mineral identification, because trace amounts of impurities can cause the same mineral to appear in very different colors

Some common color-causing mechanisms include radioactivity, which produces smoky tones, while red is produced by trace amounts of Iron and and green colorations are produced by trace amounts of Copper in the crystal structure

Streak

the color of a mineral in its powdered form

Hardness

a mineral's resistance to being scratched

Density

measures the weight of a mineral per unit volume and can help distinguish minerals that look similar

Striations

growth planes on the surface of the mineral, do not permeate through mine

Silicates

(SiO4)-4

Quartz SiO2

Feldspar NAAlSi3O8: Plag, CaAl2Si2O8: Anorthite, KAlSi3O8: Orthoclase (what makes the ocean salty)

Oxides

O-2 

• Contain oxygen, tend to rust 

Carbonates

(CO3)-2 

• Limestone  

Sulfates

(SO4) -2

Phosphates

(PO4)-3

Native Metals

Cu, Au, Ag

Neosilicates

simple crystal structure

Tectosilicates

Crystal structure is complex

Minerals become harder

Quartz

Industrial minerals

are non-metallic minerals extracted for their physical or chemical properties rather than for a specific element they contain