Mineralogy 1 ~ Midterm 1

define a mineral

naturally occurring, inorganic, crystalline solid with a definite chemical comp.

What controls mineral classification?

dominant anion or anionic group

What allows small variations in mineral chemistry?

Solid solution between similar ions

Are all rocks made of minerals?

No, coal and obsidian aren’t

Mineral species vs. Group?

Species = distinct mineral; group = related species

How does electron loss/gain affect charge?

lose an election, gain cation; gain election, gain anion

5 main bond types?

ionic, covalent, metallic, van der waals, hydrogen

Ionic vs. covalent bond property difference?

ionic = brittle; covalent = hard & strong

Why does ionic radius vary?

coordination number and charge

which ion has CN=12 with O^-2?

K^+

What do higher P and T do to substitution?

P favors small ions; T allows more variability

Goldschmidt’s first rule?

Ionic radii must differ by 15%

Example of simple substitution?

Mg²+ and Fe²+ in olivine

What promotes nucleation?

undercooling and high supersaturation.

Why small crystals in extrusive rocks?

rapid cooling = many nuclei = small crystals

define polymorphs

Same chemistry, different crystal structure

Pseudomorph example?

limonite replacing pyrite

3 polymorphism types

displacive, reconstructive, order-disorder

What does metamict mean

radiation-damaged, amorphous mineral

5 silicate structures and Si:O ratios

Isolated 1:4, Single chain 1:3, Double 4:11, Sheet 2:5, Framework 1:2

Unit cell definition?

Smallest repeating 3D unit of a crystal lattice

6 crystal systems?

Cubic, tetragonal, orthorhombic, hexagonal, monoclinic, triclinic.

Miller indices for planes?

hkl); directions = [uvw].

Refraction vs reflection?

Refraction bends light; reflection bounces it

Isotropic vs anisotropic minerals?

Isotropic = same in all directions (cubic); anisotropic = varies (quartz).