Introduction to Minerals Earth Science Introduction to Minerals

What are minerals? A mineral is a naturally occurring, homogeneous solid of definite chemical composition. It has a clear arrangement of its atoms and is formed by inorganic processes. Most of these have specific atomic structures which can be discerned by studying the outward shape of the mineral (crystal structure). These reflect the arrangement of the atoms involved in forming the mineral.

Minerals, cont. Minerals must occur naturally; coal, amber, obsidian are not minerals. It has a chemical formula…this can have some variability due to impurities of other elements, which frequently impart different colors.

Minerals, cont. Since each mineral has its own atomic make-up, each will also have its own collection of physical properties, unique to itself. Properties: Hardness (Moh’s scale, relative list) Luster Color Shape Density Fracture or cleavage Streak

Interesting Twists Polymorphs: same composition, different structures Graphite, Diamond Quartz, Tridymite, Cristobalite, Coesite Calcite, Aragonite Pyrite, Marcasite Isomorphs: same structure, different compostion Olivine: series of Mg-Fe silicates Calcite and Rhodochrosite: Ca or Mn carbonate Apatite series: hydroxyl-or fluoro-phosphate of calcium

Some Familiar Minerals: Quartz SiO2

Pyrite: FeS2

Calcite: CaCO3

Halite: NaCl

Gypsum: CaSO4-2(H2O)

Beryl: Al2Be3(Si6O18)