2. Oxide minerals
Optical properties
Reflection and refraction
Luster
Light transmission (Diaphaneity)
Colour and streak
Optical properties of common oxide ore
minerals
3. The oxide and hydroxides ,includes
compounds in which atoms or cation,
typically of one or more metals,are
combined with oxygen.
In some cases, hydrogen is one of the
cation and is present as hydroxyl or as
water of hydration
4. The optical properties of mineral comprise a wide
variety of phenomena.There are,
Reflection and refraction,
Luster,
Light transmission (Diaphaneity),
Colour and streak.
5. Reflection is the change is direction of a
wavefront at an interface between two
different media so that the wavefront returns
into the medium from which it orginated.
Refraction is the change in direction of a
wave passing from one medium to another
caused by its change in speed.
6. Luster, an optical property closely related to
reflection and refraction , can be defined as the
appearance of a material in refracted light.
Its mainly classed into two types, there are,
* Metallic luster,
* Non-metallic luster.
7. The degree to which a material transmits
light is generally termed “Diaphaneity”.
A few people in correctly call this
property “opacity”.
*Transparent,
*Translucent,
*Opaque.
8. The colour of light is commonly said
to depend upon its wave length.
The colour of the mineral powder its
called streak.
9. Oxides minerals
The oxides are classified conveniently on the basis of
the A: X ratio; they are followed by the hydroxides.
Oxides
A₂X Type
Cuprite, Cu₂O
AX Type
Periclase, MgO
Zincite, (Zn, Mn)O
14. Colour-red nearly black
Streak-brownish red
Luster-submetallic to adamantine or earthy
Light Transmission-red by transmitted light,
yellow in thinner splinters
Isotropic mineral
Refractive index: n,2.849
16. Colour and Streak:Deep red to yellow
Luster:Subadamantine
Diaphaneity: Translucent
Anisotropic mineral, uniaxial (+)
Refractive indices:w,2.013; e,2.029
Birefringence:0.0160
17. 1.Spinel,MgAl2O4
Colour and Streak: various, ranges from red
to blue, green, brown and nearly colourless
Luster: vitreous
Diaphaneity: transparent to subtranslucent
Isotropic mineral
Refractive index: n,1.719
18. Colour and Streak: Black
Luster: Splendent to dull metallic
Diaphaneity: Opaque
Isotropic mineral
Refractive index: 2.42
19. Colour and Streak: Black and brown
Luster: Metallic
Diaphaneity: Almost opaque
Isotropic mineral
Refractive index: 2.08-2.16
20. Colour and Streak: Black to brownish
black. Reddish brown
Luster: Metallic to submetallic
Diaphaneity: Opaque, translucent in fine
fragments
Refractive index: 2.36
Isotropic mineral
21. Colour and Streak: Brownish
black.Chestnut brown
Luster: Submetallic
Light Transmission: Almost opaque
Anisotropic mineral, uniaxial (-)
Refractive indices: w,2.46; e,2.15
Birefringence: 0.31
23. 1.Corundum, Al2O3
Some crystals are colour zoned, pure Al2O3 is
white
Luster: Submetallic to splendent to vitreous
Light Transmission: Transparent to translucent
Anisotropic mineral, uniaxial (-)
Refractive indices: w,1.767-1.772; e,1.759-
1.762
24. Colour and Streak: Dull to bright red, steel
grey. Red-brown
Luster: Metallic to submetallic
Light Transmission: Transmitted light
Anisotropic, uniaxial (-)
Refractive indices: w,3.15-3.22; e,2.87-2.94
Pleochroism present, yellow and red brown
25. Colour and Streak: Iron black.Black
Luster: Metallic to submetallic
Light Transmission: Nearly opaque
Anisotropic, uniaxial (-)
Refractive indices: w,2.7
26. 1.Rutile, TiO2
Colour and Streak: Pure TiO2 is white.( Reddish
brown, rarely yellowish)
Luster: Adamantine to metallic
Light Transmission: Nearly opaque but transparent in
thin pieces
Anisotropic, uniaxial (+)
Refractive indices: w,2.065-2.616; e,2.890-2.903
27. Colour and Streak: White, yellow or red brown
to brown- black.Greyish white or brownish
streak
Luster: Adamantine and splendant
Transparency: coloured minerals are transparent
Anisotropic, uniaxial (+)
Refractive indices: w,1.990-2.010; e,2.091-
2.100
Pleochroism present, coloured zone