Physical properties of minerals

a. Color

• Calcite has more colours
• Sulfur and Pyrite have same colour

b. Streak

• Refers to the colour of the powder form of the mineral.
• Hematite – red
• Magnetite – Black
• Talc – white

c. Fracture and Cleavage

• Describe the way a mineral breaks
• Conchoidal – curved surface
• Uneven – Uneven surface
• Hackly – Jagged surface
• Earthy – Like chalk
• Even – Smooth

d. Cleavage:

• Some minerals break along certain well defined planes called cleavage planes.
• Gypsum – 1 set
• Calcite – 2 sets
• Flourite – 3 sets

e. Luster:

• The way a mineral reflects light Metallic (Magnetite); Sub-metallic, Vitreous (Opal), Resinous (Pyrite), Pearly, Adamentine (Diamond), silky (Asbestos) and greasy.

f. Crystal form:

• Crystal structure is the result of regular grouping of atoms that are homogeneous. A crystal is a polyhedral form, which means it is a geometric solid. It has a specific set of faces, corners and edges, which is consistent with the geometric packing of the atoms.
• There are 6 basic crystal forms

1. Isometric
2. Tetragonal
3. Hexagonal
4. Orthorhombic
5. Monoclinic
6. Triclinic

g. Taste:

• This property is used to identify the mineral halite (salt)

h. Specific Gravity:

• This characteristic relates to the minerals density. If the mineral is heavy for its size, then it has a high specific gravity

I. Magnetism:

• Is the mineral magnetic (try using a compass), or is it attracted by a magnet? This property is characteristic of Magnetite.

j. Effervescence:

• When some minerals are exposed to acids, they begin to fizz (calcite).

k. Birefringence:

• This is also known as double refraction. Birefringent minerals split the light into two different rays which gives the illusion of double vision in this Iceland Spar Calcite

l. Fluorescence:

• Some minerals display the phenomenon of photoluminescence.