Introduction to Mineralogy Mineralogy is a mixture of: Mineralogy is a mixture of: New concepts – much of it from chemistry and physics with a geologic point of view New concepts – much of it from chemistry and physics with a geologic point of view Fairly complex ideas (but not insurmountable) Fairly complex ideas (but not insurmountable) New vocabulary – many terms New vocabulary – many terms Large amounts of memorization Large amounts of memorization This mixture can make mineralogy seem a bit complicated and esoteric This mixture can make mineralogy seem a bit complicated and esoteric

So why mineralogy? Minerals are chemical compounds that form from natural earth processes Minerals are chemical compounds that form from natural earth processes Minerals are basic building blocks of rocks Minerals are basic building blocks of rocks Rocks provide record of earth history and are formed by earth processes Rocks provide record of earth history and are formed by earth processes Geologists Geologists Study earth history Study earth history Study earth processes Study earth processes Mineralogy is the key. Mineralogy is the key.

Objectives Three parts to class (originally three classes): 1. Learn chemical properties of minerals Crystallography – spatial arrangement of atoms Crystallography – spatial arrangement of atoms Crystal chemistry – what atoms make up minerals and why Crystal chemistry – what atoms make up minerals and why

2. Analytical methods: Physical properties (this week’s lab) – visual observations Physical properties (this week’s lab) – visual observations Polarizing microscope Polarizing microscope X-ray diffraction X-ray diffraction 3. Identify, classify and organize minerals

Definition of Mineral A naturally occurring, homogeneous solid, with a defined (but generally not fixed) chemical composition and an ordered atomic arrangement

1. Naturally occurring Why not synthetic (man-made)? Why not synthetic (man-made)? E.g. diamonds E.g. diamonds Corian countertops (quartz) Corian countertops (quartz) Table salt (halite) Table salt (halite) Others? Others? San Francisco Bay Salar de Uyuni, Bolivian Altiplano

2. Homogeneous solid Minerals can not be PHYSICALLY broken into new compounds Minerals can not be PHYSICALLY broken into new compounds How about chemically “broken”? How about chemically “broken”? What would they break into? What would they break into? Why solid? Why solid? Chemical reaction: Albite → Na + + Al 3+ + SiO 4 4- Physical Reaction: Big Feldspar → Little Feldspar

3. Defined, but not fixed, composition The compositions of minerals are strictly defined (stoichiometry), but can vary between compositions The compositions of minerals are strictly defined (stoichiometry), but can vary between compositions For example: For example: Calcite is CaCO 3 but will also contain much Mg, Sr, Fe, Mn etc. Calcite is CaCO 3 but will also contain much Mg, Sr, Fe, Mn etc. Olivine - (Fe,Mg) 2 SiO 4 - is a group of two main minerals: Olivine - (Fe,Mg) 2 SiO 4 - is a group of two main minerals: Fayalite (Fe 2 SiO 4 ) Fayalite (Fe 2 SiO 4 ) Forsterite (Mg 2 SiO 4 ) Forsterite (Mg 2 SiO 4 )

4. Ordered atomic arrangement Crystallography – how atoms are arranged in space. Crystallography – how atoms are arranged in space. For example: For example: Aragonite (CaCO 3 ) and calcite (CaCO 3 ) are different minerals but have identical compositions Aragonite (CaCO 3 ) and calcite (CaCO 3 ) are different minerals but have identical compositions This is why minerals are referred to by name rather than formula This is why minerals are referred to by name rather than formula Mineral names include both composition (chemistry) and crystallography Mineral names include both composition (chemistry) and crystallography