Mineral names and compositions

Question 1

Olivine end members

Answer 1

Forsterite (Mg)
Fayalite (Fe)

Question 2

General olivine formula

Answer 2

[Mg, Fe]2 Si O4

Question 3

pyroxene general formula

Answer 3

X Y Si2 O6

Question 4

types of orthopyroxene

Answer 4

Enstatite (Mg)
Ferrosilite (Fe)

Question 5

types of clinopyroxene

Answer 5

Diopside (Ca Mg)
Hedenbergite (Ca Fe)

Question 6

What ions form the 3 points on the pyroxene ternary diagram

Answer 6

Mg, Fe, Ca

Question 7

Name for orthopyroxene with small amount of Ca

Answer 7

Pigeonite

Question 8

Name for cpx with <50% Ca

Answer 8

Augite

Question 9

What happens to bond length and crystal structure with increasing temperature

Answer 9

Atoms vibrate further away from their equilibrium position = repulsion between nuclei at greater distances.

Minimum potential energy occurs at greater distance between atoms => increase bond length

Therefore increase volume

Question 10

What happens to crystal structure with increasing pressure

Answer 10

repulsion between nuclei = bond length not shortened much

displacive phase transition

reconstructive phase transition

Question 11

types of phase transition
with examples

Answer 11

displacive phase transition
- tetrahedra rotate
- decreases symmetry
- alpha <-> beta quartz

reconstructive phase transition
- break bonds
- rotate
-reform new bonds
- tridymite <-> cristobalite