Lecture 10: Crystal Structures and Solid Solutions Read Chpt 2

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Solid Solutions: Substitutional Solid Solution Olivine is an example of a: Simple Substitution: trade ions of the same charge, , e.g., Fe +2 for Mg +2 or Al +3 for Fe +3 It is also possible to have: Coupled Substitution: trade ions of different charges; need to trade pairs to maintain electroneutrality Example: Ca +2 + Al +3 = Na + + Si +4 This is common in feldspars. NaAlSi 3 O 8 (albite)) to CaAl 2 Si 2 O 8 (anorthite) But you can maintain neutrality another way, too: Ex. Na + + Al +3 = Si +4 + EMPTY SITE
Solid Solutions: This is an example of… Ex. Na + + Al +3 = Si +4 + EMPTY SITE 2. Omission solid solution: highly charged cation replaces two or more other cations, , leaving structural vacancies Example: Pyrrhotite (Fe (Fe 1-x S) Note: if all sites were full, would be FeS, , instead, some Fe sites are vacant and some have Fe +3 to compensate for the missing Fe +2
Page 1 and 2: Lecture 10: Crystal Structures and
Page 3 and 4: Many minerals share the same geomet
Page 9: Some Common Structure Types CsCl St
Page 15: Some Common Structure Types CaF 2 S
Page 18 and 19: Solid Solutions 1. Substitutional S
Page 22 and 23: Solid Solutions: Last type of solid

Lecture 10: Crystal Structures and Solid Solutions Read Chpt 2

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