The pyroxene group of minerals03

5,817 views

Published on

0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
5,817
On SlideShare
0
From Embeds
0
Number of Embeds
1
Actions
Shares
0
Downloads
214
Comments
0
Likes
3
Embeds 0
No embeds

No notes for slide

The pyroxene group of minerals03

  1. 1. THE PYROXENE GROUP OF MINERALS
  2. 3. The Pyroxene Group
  3. 4. Silicate Structure Of Pyroxenes <ul><li>The pyroxene group of minerals is in the INOSILICATE subdivision of the silicates group </li></ul><ul><li>Inosilicates  - Group of silicate minerals that have their tetrahedrons form single or multiple chains, with two oxygen atoms of each tetrahedron part of its neighboring tetrahedron forming long, thin, chains. Si: O =1:3. </li></ul>
  4. 5. INOSILICATE STRUCTURE <ul><li>Divided into two types: </li></ul><ul><li>Single Chain Structure </li></ul><ul><li>Double Chain Structure </li></ul>
  5. 7. Silica tetrahedrons
  6. 8. Single Chain Inosilicate Structure
  7. 9. Double Chain Inosilicate Structure
  8. 12. <ul><li>This difference produces a difference in angles </li></ul><ul><li>The cleavage of the two groups results between chains and does not break the chains thus producing prismatic cleavage </li></ul><ul><li>In the single chained silicates the two directions of cleavage are at 87° and 93° (close to 90 degrees) forming nearly square cross sections </li></ul><ul><li>In the double chain silicates the cleavage angles are at 56° and 124° (close to 120 and 60 degrees) forming rhombic cross sections </li></ul>
  9. 13. <ul><li>This makes it a convenient way to distinguish between single chain and double chain silicates or more precisely between pyroxene minerals and amphibole minerals </li></ul><ul><li>The amphiboles contain the same elements that the pyroxenes do, except they have hydroxyl (OH) in their structure, which alters both its physical and chemical properties </li></ul><ul><li>For example:- </li></ul><ul><li>Augite- (Ca,Mg,Fe)SiO 3 </li></ul><ul><li>Hornblende- Ca 2 (Mg, Fe, Al) 5  (Al, Si) 8 O 22 (OH) 2 </li></ul>
  10. 15. Clino pyroxene group <ul><li>Clino pyroxene (Diopside series) </li></ul><ul><li>Diopside Ca Mg Si2 O6 </li></ul><ul><li>Hedenbergite Ca Fe Si2 O6 </li></ul><ul><li>Pyroxene Solid solutions </li></ul><ul><li>Pigeonite (Ca, Mg, Fe)2 Si2 O6 </li></ul><ul><li>Augite (Ca, Mg, Fe, Na) (Mg, Fe, Al) (Si, Al)2 O6 </li></ul><ul><li>Omphacite (Ca, Na )(Fe Mg Al) (Si, Al)2 O6 </li></ul><ul><li>Aegirine Na (Al, Fe3+) Si2 O6 </li></ul><ul><li>Na and Li pyroxenes </li></ul><ul><li>Jadeite Na Al Si2 O6 </li></ul><ul><li>Spodumene Li Al Si2 O6 </li></ul>
  11. 16. General formula (w,x,y)2 Z2 O6 <ul><li>In which w, x, y, z indicate elements having similar ionic radii and capable of replacing each otherin the structure. </li></ul><ul><li>W= Ca, Na </li></ul><ul><li>X= Mg, Fe2+, Mn, Li </li></ul><ul><li>Y= Al, Fe 3+, Ti </li></ul><ul><li>Z= Si, Al </li></ul>
  12. 17. Diopside- hedenbergite <ul><li>Complete solid solution exist between diopside and hedenbergite and johannssenite (Ca Mn Si2 O6) </li></ul><ul><li>Diopside is the most common pyroxene. Found in mafic and ultramafic igneous rocks. </li></ul><ul><li>Found in marbles associated with calcite, quartz or forsterite, tremolite and garnet. </li></ul><ul><li>Also found in medium and high grade metamorphosed mafic rocks. </li></ul><ul><li>Hedenbergite is often found associated with ore deposits formed at high temperatures </li></ul>
  13. 18. AUGITE
  14. 19. AEGIRINE
  15. 20. DIOPSIDE
  16. 22. Enstatite- Ferrosilite <ul><ul><li>Enstatite Mg Si O3 </li></ul></ul><ul><ul><li>Ferrosilite FeSiO3 </li></ul></ul><ul><ul><li>Hypersthene& Bronzite (Mg, Fe)2 Si2 O6. </li></ul></ul><ul><ul><li>Enstatite usually massive , blocky, fibrous or lamellar. Individual crystals may be prismatic or acicular. </li></ul></ul><ul><ul><li>Complete solid solution exist between Enstatite- Ferrosilite </li></ul></ul><ul><ul><li>Except at high temperature, only limited solid solution exist between clino pyroxene end members diopside and heldenbergite. </li></ul></ul>
  17. 23. <ul><li>Enstatite- Ferrosilite </li></ul><ul><li>Enstatite 0-10(% Fe) </li></ul><ul><li>Bronzite 10-30 </li></ul><ul><li>Hypersthene 30-50 </li></ul><ul><li>Ferrohypersthene 50-70 </li></ul><ul><li>Eulite 70-90 </li></ul><ul><li>Orthoferrosilite 90-100 </li></ul>
  18. 24. Occurrence and associations <ul><li>Enstatite is more common in mafic igneous rocks. </li></ul><ul><li>Commonly associating with plagioclase and clinopyroxene </li></ul><ul><li>Also in high- grade metamorphic rocks and is considered diagnostic for the granulite facies . </li></ul><ul><li>Hypersthene is a characteristic mineral associated with charnockite series of rocks. </li></ul><ul><li>Eulite and Orthoferrosilite- associated with fayalite, hedenbergite, grunerite and almandine – spessartine garnet, of eulysite, a regionally metamorphosed Iron rich sediment. </li></ul>
  19. 25. Augite <ul><li>Most common pyroxene found in mafic to intermediate igneous rocks, both plutonic and volcanic </li></ul><ul><li>Associated with hornblende and plagioclase </li></ul><ul><li>Augite is equivalent to diopside with may impurities, especially Na. </li></ul><ul><li>Omphacite is a bright green variety of augite rich in Na and Al. </li></ul>
  20. 26. Jadeite <ul><li>The term jade refers to either jadeite or to the amphibole, nephrite. </li></ul><ul><li>It is a high pressure pyroxene found in metamorphic rocks of the blueschist facies. </li></ul><ul><li>Associated with glaucophane, lawsonite or aragonite, and with quartz and epidote. </li></ul><ul><li>A bright green variety of jadeite, omphacite, occurs in eclogites with pyrope rich garnets. Omphacite is also found in kimberlites. </li></ul>
  21. 27. Spodumene <ul><li>Spodumene found in granitic pegmatites, where it associated with k- feldspar, quartz, muscovite, tourmaline, beryl and lepidolite. </li></ul><ul><li>Hiddenite is a name given to emerald green spodumene. </li></ul><ul><li>Kunzite to lilac/pink colour spodumene. </li></ul><ul><li>Triphane to colourless or yellow spodumene. </li></ul>
  22. 28. ENSTATITE
  23. 29. FERROSILITE
  24. 30. HYPERSTHENE
  25. 31. THE END

×