Group B - Mineralogy Part 1

5 SYMMETRY ELEMENTS OF CRYSTALLOGRAPHIC SYSTEMS

1. IDENTITY

2. PROPER AXIS/ROTATIONAL AXIS OF SYMMETRY

3. PLANE OF SYMMETRY/MIRROR PLANE

4. CENTER OF SYMMETRY/INVERSION CENTER

5. ROTOINVERSION

1. IDENTITY

Simplest symmetry element.

Corresponds to the operation of doing nothing to the object.

2. PROPER AXIS/ROTATIONAL AXIS OF SYMMETRY

An imaginary line passing through the center of mass around which is a rotation by 360 degrees leaves an object in an orientation indistinguishable from the original.

3. PLANE OF SYMMETRY/MIRROR PLANE

an imaginary plane divides the crystal in two parts in such a way that one part is mirror of the other, the crystal is said to have a plane of symmetry. Reflection Operation: two parts on an object after reflection through the plane produce the indistinguishable orientation.

4. CENTER OF SYMMETRY/INVERSION CENTER

The ______ of symmetry is such a point that any line drawn through it touches the surface of the crystal at equal distance in both directions.

5. ROTOINVERSION

A combination of rotation with a center of inversion.

SEVEN CRYSTAL SYSTEMS IN CRYSTALLOGRAPHY

1. ISOMETRIC (CUBIC)

2. TETRAGONAL

3. ORTHORHOMBIC

4. HEXAGONAL

5. TRICLINIC

6. MONOCLINIC

7. RHOMBOHEDRAL (TRIGONAL)

1. ISOMETRIC (CUBIC)

all three axes are equal in length and all are perpendicular to one another.

2. TETRAGONAL

two of the three axes are equal in length and all three axes are perpendicular to one another.

3. ORTHORHOMBIC

all three axes are unequal in length and all are perpendicular to one another.

4. HEXAGONAL

Of four axes three are equal in length, are separated by equal angles and lie in the same plane. The fourth axis is perpendicular to the plane of the other three axes. Hexagonal cells have lattice points in each of the two sixsided faces.

5. TRICLINIC

All three axes are unequal in length and none is perpendicular to another.

6. MONOCLINIC

All three axes are unequal in length and two axes are perpendicular to each other.

7. RHOMBOHEDRAL (TRIGONAL)

all three axes of equal length and none of the axes is perpendicular to another but the crystal faces all have the same size and shape.

PHYSICAL PROPERTIES OF MINERALS

1. COLOR

2. STREAK

3. LUSTER

4. SPECIFIC GRAVITY

5. HARDNESS

6. CLEAVAGE

7. FRACTURE

8. CRYSTAL SHAPE

9. TENACITY

10. MAGNETISM

11. FLOURECENCE AND PHOSPHORESCENCE

1. COLOR

The visible ____ that a mineral sample appears to the naked eye.

is NOT A RELIABLE characteristic to use for mineral identification.

2. STREAK

is tested by rubbing a sample against an unglazed ceramic streak plate.

3. LUSTER

The way in which light reflects off of a mineral’s surface.

4. SPECIFIC GRAVITY

compares the density of the mineral to the density of the same amount of water.

5. HARDNESS

is the strength with which a mineral resists its surface being scraped or punctured.

6. CLEAVAGE

is the easily breakable plane along which the atoms are closely packed.

7. FRACTURE

is developed in a mineral by a sharp blow with a hard object

8. CRYSTAL SHAPE

shape of a ____ follows the symmetry of its lattice

9. TENACITY

a mineral's ability to resist deformation, breaking, or being altered when subjected to stress.

10. MAGNETISM

react when placed within a ______ field.

11. FLOURECENCE

that light up when exposed to ultraviolet light, x-rays, or cathode rays

11. PHOSPHORESCENCE

emission of light continues after the light is cut off,

Hardness Scale

Mohs

There are two main types of Luster:

Metallic and non-metallic

TYPES OF NON-METALLIC LUSTERS:

ADAMANTINE

VITREOUS

PEARLY

SILKY

RESINOUS

GREASY

ADAMANTINE

transparent to translucent and the shiniest of the non-metallics

VITREOUS

resembles a freshly cleaned pane of glass, transparent to translucent with a low refractive index

PEARLY

resembles the iridescence

SILKY

composed of thin parallel fibers

RESINOUS

resembles hardened maple syrup or frozen pine resin

GREASY

appear as though covered in a thin layer of oil.