Thomas chinnappan geologist keeranur, pudukkottai, tamilnadu, india.

1. BY:
THOMAS CHINNAPPAN . A ,
M.SC.APPLIED GEOLOGY,
PERIYAR UNIVERSITY,
SALEM.

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

10.  Spinel Group
 Spinel, MgAl₂O4,
 Magnetite, FeFe₂O4
 Chromite, FeCr₂O4.
 Franklinite, (Zn,Mn, Fe)(Fe, Mn)₂O4
 Hausmannite, MnMn₂O4
 Chrysoberyl, BeAl₂O4

11.  Hematite Group
 Corundum, Al₂O3,
 Hematite, Fe₂O3,
 Ilmenite, FeTiO3,
 Braunite, 3Mn₂O3.MnSiO3.

12.  Rutile Group
 Rutile, TiO₂
 Cassiterite, SnO₂
 Pyrolusite, MnO₂

13.  Brucite, Mg(OH)₂
 Gibbsite, Al(OH)3
 Boehmite, AlO(OH)
 Manganite, MnO(OH)
 Diaspore, AIO(OH)
 Goethite, FeO(OH)

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

15.  Colour-colourless
 Streak-white
 Luster-vitreous
 Diaphaneity-transparent
 Isotropic mineral
 Refractive index: n,1.735-1.745

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

22.  Colour and Streak: Green, greening white,
yellowish green.White
 Luster: Vitreous
 Light Transmission: Transparent
 Anisotropic mineral, biaxial (+)
 Refractive indices: a,1.732-1.747; b,1.734-
1.749;g,1.741-1.758
 Slightly pleochroic

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

28.  1.Goethite, FeO(OH)
 Colour and Streak: Brownish yellow to orange
yellow
 Luster: Adamantine, metallic to dullLight
 Transmission: Transparent
 Anisotropic, biaxial (-)
 Refractive indices: a,2.260-2.275; b,2.393-
2.409; g,2.398-2.515