Lecture 6 OVERVIEW

Details

Crystal growth, Physical properties of minerals

Crystallization

Crystal nucleation

Crystal growth

Crystal imperfections

Defects

Point defects

Impurity defects

Paired vacancies

Line defects

edge dislocation

screw dislocation

Stacking faults

Zoning

Twinning

simple twins

multiple twins

contact twins

penetration twins

Physical properties of minerals

HAND SPECIMEN PROPERTIES

1. Appearance

LUSTER

DIAPHENITY

COLOR

Allochromatic minerals

Idiochromatic minerals

STREAK

LUMINESCENCE

COLOR PLAY

2. Crystal shape

3. Strength – related primarily to bonding

TENACITY

CLEAVAGE, FRACTURE, PARTING

HARDNESS

4. Density (specific gravity)

5. Magnetism

ANISOTROPY AND PHYSICAL PROPERTIES

DIRECTIONAL PROPERTIES

thermal conductivity relates heat flow to temperature gradient

electrical conductivity relates electrical current density to electric field

diffusivity relates atomic flux to concentration gradient

elastic properties relate strain (extent of deformation) to applied stress

seismic properties relate to velocity of seismic wave propagation (related to density, rigidity, bulk modulus)

optical properties relate to refractive index variations

Physical properties may be

isotropic – uniform in all directions (isometric crystals)

uniaxial – similar in two directions and different in the third (hexagonal and tetragonal crystals)

biaxial – different in all three directions (orthorhombic, monoclinic, trigonal crystals)