Optical properties of common oxide ore minerals in economic geology
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This document discusses the optical properties of common oxide ore minerals. It defines properties like reflection, refraction, luster, light transmission, color, and streak. It then examines these properties for specific oxide minerals like hematite, magnetite, corundum, rutile, and goethite. For each mineral, it provides details on their color, streak, luster, transparency, crystal structure, and refractive index. The document serves as a guide to identifying oxide minerals based on their optical characteristics under reflected light microscopy.
Optical properties of common oxide ore minerals in economic geology
- 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