1. Geotechnics and applied geology – Civil Engineering Department V.V.P. Engineering College, Rajkot Enrolment No: Chavda Laksha

2. Mineralogy & Petrology

5. PHYSICAL PROPERTIES

6. Minerals have distinctive physical properties that geologists use to identify and describe them.
There are 8 major physical properties of minerals:
1. Color
2. Luster
3. Form And Structure
4. Cleavage
5. Fracture
6. Hardness
7. Specific Gravity
8. Streak

12. Quartz

17. Luster refers to how light is reflected from the surface of a mineral
There are two main types of luster: metallic and non-metallic:
Minerals with a metallic luster are described as shiny, silvery, or having a metal-like reflectance.
Non-metallic minerals may be described as resinous, translucent, pearly, waxy, greasy, silky, vitreous/glassy, dull, or earthy
Luster may be subjective, and thus is not always a reliable identifier

22. 3.Form And Structure
The term used to describe general shape of a crystal is habit.
Some common crystal habits are as follows :
Individual Crystals
Cubic - cube shapes
Octahedral - shaped like octahedrons.
Tabular - rectangular shapes.
Equant - a term used to describe minerals that have all of their boundaries of approximately equal length.
Acicular - long, slender crystals.
Prismatic - abundance of prism faces.
Bladed - like a wedge or knife blade.

23. bladed
globular
accicular
Octahedron
Dodecahedron
cubic

24. Groups of Distinct Crystals.
Radiated - radiating groups of crystals.
Fibrous - elongated clusters of fibers.

25. Equant
Fibrous
dendritic
Prismatic
Reticulated
Drusy

26. 4.Cleavage
Cleavage refers to the tendency of a mineral to break along planes of weakness in the chemical bonds, or along planes where bond strength is the least.
Some minerals break along one dominant plane of cleavage producing parallel sheets, where as others may break along two or more planes of cleavage, producing blocks or prism shapes.

27. Cleavage is described by:
Cleavage: tendency of a mineral to break along planes of weakness
Cleavage is described by:
Number of planes
Angles between adjacent planes

29. Physical Properties of Minerals
Cleavage (1 direction):
Example: mica

30. Physical Properties of Minerals
Cleavage (2 directions):
orthoclase
amphibole

31. Physical Properties of Minerals
Cleavage (3 directions):
halite
calcite

32. Cleavage, cont. Feldspar: Two Cleavage Planes
One direction of cleavage (one plane)
Mineral Example: Micas (muscovite)
Two directions of cleavage (two planes)
Mineral Example: Feldspar
Three directions of cleavage (three planes)
Cubic : Mineral Example: Galena
Rhombohedral: Mineral Example: Calcite
Four directions of cleavage (four planes)
Mineral Example: Flourite
Courtesy United States Geological Survey
plane one:
plane two:
Feldspar: Two Cleavage Planes
Galena: Three Cleavage Planes
Plane one:
Plane two:
Plane three:
Copyright©Dr.Richard Busch
Calcite: Three Cleavage Planes
Plane one:
Plane two:
Plane three:
Copyright©Stonetrust, Inc

33. 5.Fracture Fracture refers to the non-planar breakage of minerals.
Minerals that break along fractures (as oppose to cleavage planes) do not exhibit predictable weakness along specified bonds.
Fractures may be described as splintery, uneven, or conchoidal.
If the mineral contains no planes of weakness, it will break along random directions called fracture. Several different kinds of fracture patterns are observed.
Conchoidal fracture - breaks along smooth curved surfaces.
Fibrous and splintery - similar to the way wood breaks.
Hackly - jagged fractures with sharp edges.
Uneven or Irregular - rough irregular surfaces.

34. Conchoidal Fractures on a Quartz Mineral

38. Hardness is determined by scratching the mineral with a mineral or substance of known hardness.
Hardness is a relative scale, thus to determine a mineral's hardness, you must determine that a substance with a hardness greater than the mineral does.
Hardness is determined on the basis of Moh's relative scale of hardness exhibited by some common minerals.
These minerals are listed below, along with the hardness of some common objects.
Testing mineral hardness. The harder mineral (quartz) scratches the softer one (calcite).

41. 7.Specific Gravity
Specific gravity refers to the weight or heaviness of a mineral, and it is expressed as the ratio of the mineral’s weight to an equal volume of water.
Water has a specific gravity of 1. Therefore, a mineral with a specific gravity of 1.5, is one and a half times heavier than water.
Minerals with a specific gravity < 2 are considered light, 2-4 are average, and >4.5 are heavy
Specific gravity can be measured using complex lab tools such as the hydrostatic balance

42. 8.Streak
Streak refers to the color of a mineral’s powdered form left behind after it is scraped or rubbed across a porcelain streak plate.
A mineral may appear one color and then produce a streak with a different color.
A mineral’s streak color is a more reliable identification characteristic than the minerals perceived surface color.
Even though the mineral pyrite is
gold in color, it leaves a grey “pencil lead” streak on the porcelain streak plate.